Delaware River
The Delaware River flowing through the Delaware Water Gap, which divides New Jersey and Pennsylvania, in 2021
Map of the Delaware River watershed, showing major tributaries and cities
Location
Country	United States
State	New York, New Jersey, Pennsylvania, Delaware, and Maryland, U.S.
Cities	Margaretville, NY, Delhi, NY, Deposit, NY, Hancock, NY, Callicoon, NY, Lackawaxen, PA, Port Jervis, NY, Stroudsburg, PA, Easton, PA, New Hope, PA, Trenton, NJ, Camden, NJ, Philadelphia, PA, Chester, PA, Wilmington, DE, Salem, NJ, Dover, DE
Physical characteristics
Source	West Branch
• location	Mount Jefferson, Town of Jefferson, Schoharie County, New York, United States
• coordinates	42°27′12″N 74°36′26″W / 42.45333°N 74.60722°W / 42.45333; -74.60722
• elevation	2,240 ft (680 m)
2nd source	East Branch
• location	Grand Gorge, Town of Roxbury, Delaware County, New York, United States
• coordinates	42°21′26″N 74°30′42″W / 42.35722°N 74.51167°W / 42.35722; -74.51167
• elevation	1,560 ft (480 m)
Source confluence
• location	Town of Hancock, Delaware County, New York, United States
• coordinates	41°56′20″N 75°16′46″W / 41.93889°N 75.27944°W / 41.93889; -75.27944
• elevation	880 ft (270 m)
Mouth	Delaware Bay
• location	Delaware, United States
• coordinates	39°25′13″N 75°31′11″W / 39.42028°N 75.51972°W / 39.42028; -75.51972
• elevation	0 ft (0 m)
Length	301 mi (484 km)
Basin size	13,539 sq mi (35,070 km2)
Discharge
• location	Trenton
• average	12,100 cu ft/s (340 m3/s)
• minimum	4,310 cu ft/s (122 m3/s)
• maximum	329,000 cu ft/s (9,300 m3/s)
Discharge
• location	Port Jervis
• average	7,900 cu ft/s (220 m3/s)
• minimum	1,420 cu ft/s (40 m3/s)
• maximum	52,900 cu ft/s (1,500 m3/s)
Basin features
Tributaries
• left	Neversink River, Pequest River, Musconetcong River
• right	Lehigh River, Schuylkill River, Christina River
National Wild and Scenic River
Type	Scenic, Recreational

v t e Delaware River
Legend
East Branch Delaware River NY PA West Branch Delaware River Equinunk Creek Lordville–Equinunk Bridge Kellams Bridge Callicoon Bridge Cochecton–Damascus Bridge (PA 371) Skinners Falls–Milanville Bridge Narrowsburg–Darbytown Bridge (PA 652 / NY 52) Tusten Station Railroad Bridge (NS Rail) Lackawaxen River Roebling's Delaware Aqueduct Barryville–Shohola Bridge (PA 434 / NY 55) Shohola Creek Pond Eddy Bridge Mongaup River Millrift Railroad Bridge (NS Rail) Mid-Delaware Bridge (US 6 / US 209) Interstate 84 Bridge (I-84) PA NY NJ Neversink River Milford–Montague Toll Bridge (US 206) Dingman's Ferry Bridge Big Bushkill Creek (Bush Kill) Flat Brook Depew Island Poxono Island Tocks Island Depue Island Shawnee Island Brodhead Creek Schellenbergers Island Delaware Water Gap Toll Bridge (I-80 / AT) Delaware Water Gap Delaware River Viaduct Portland–Columbia Pedestrian Bridge Portland–Columbia Toll Bridge (NJ 94) Delaware, Lackawanna and Western Railroad Dildine Island Belvidere - Riverton Bridge Pequest River Foul Rift Roxburg Branch Keifer Island Martins Creek Branch Martins Creek Getters Island Bushkill Creek Easton–Phillipsburg Toll Bridge (US 22) Northampton Street Bridge Lehigh River Delaware Canal Lehigh and Hudson River Railway Central Railroad of New Jersey Bridge Lehigh Valley Railroad Interstate 78 Toll Bridge (I-78) Whippoorwill Island Raubs Island Riegelsville Bridge Musconetcong River Upper Black Eddy–Milford Bridge Uhlerstown–Frenchtown Bridge (NJ 12) Marshall Island Treasure Island Prahls Island Tohickon Creek Delaware & Raritan Canal Lumberville Wing Dam Bull's Island Paunnacussing Creek Lumberville–Raven Rock Bridge Lockatong Creek Hendrick Island Wickecheoke Creek Centre Bridge–Stockton Bridge (PA 263) New Hope–Lambertville Toll Bridge (US 202) New Hope–Lambertville Bridge (PA 179 / NJ 179) Lambertville Wing Dam Washington's Crossing Washington Crossing Bridge Scudder Falls Bridge (I-295) West Trenton Railroad Bridge WTR Rotary Island Calhoun Street Bridge To the Raritan River in New Brunswick To Bristol Assunpink Creek Lower Trenton Bridge (US 1 Bus.) Trenton–Morrisville Toll Bridge (US 1) Morrisville–Trenton Railroad Bridge TRE Falls of the Delaware Limit of tidal river and navigability Biles Creek Crosswicks Creek Newbold Island Scotts Creek Tullytown Cove Delaware River–Turnpike Toll Bridge (I-95) Burlington Island Mill Creek Assiscunk Creek Burlington–Bristol Bridge (PA 413 / NJ 413) Neshaminy Creek Mud Island Shoal Poquessing Creek Rancocas River Pennypack Creek Pompeston Creek Tacony–Palmyra Bridge (PA 73 / NJ 73) Palmyra Cove Pennsauken Creek Betsy Ross Bridge (NJ 90) Frankford Creek Delair Bridge ACL Petty Island 36th Street Bridge Cooper River Benjamin Franklin Bridge (I-676 / US 30 / PATCO) RiverLink Ferry Summer only Walt Whitman Bridge (I-76) Newton Creek Little Timber Creek Big Timber Creek Schuylkill River Woodbury Creek Little Mantua Creek Mantua Creek Little Tinicum Island Darby Creek Crum Creek Ridley Creek Chester Island Chester Creek Old Canal Commodore Barry Bridge (US 322 / CR 536) Raccoon Creek PA DE NJ Naamans Creek Oldmans Creek Shellpot Creek Christiana River Salem Canal Delaware Memorial Bridge (I-295 / US 40) Pea Patch Island Forts Ferry Crossing Summer only Branch Canal Salem River Chesapeake & Delaware Canal to the Chesapeake Bay Reedy Island Alloway Creek Delaware Bay Cape May–Lewes Ferry (US 9) Atlantic Ocean

The Delaware River is a major river in the Mid-Atlantic region of the United States and is the longest free-flowing (undammed) river in the Eastern United States. From the meeting of its branches in Hancock, New York, the river flows for 282 miles (454 km)^[1] along the borders of New York, Pennsylvania, New Jersey, and Delaware, before emptying into Delaware Bay.

The river has been recognized by the National Wildlife Federation as one of the country's Great Waters^[2] and has been called the "Lifeblood of the Northeast" by American Rivers.^[3] Its watershed drains an area of 13,539 square miles (35,070 km²) and provides drinking water for 17 million people, including half of New York City via the Delaware Aqueduct.

The Delaware River has two branches that rise in the Catskill Mountains of New York: the West Branch at Mount Jefferson in Jefferson, Schoharie County, and the East Branch at Grand Gorge, Delaware County. The branches merge to form the main Delaware River at Hancock, New York. Flowing south, the river remains relatively undeveloped, with 152 miles (245 km) protected as the Upper, Middle, and Lower Delaware National Scenic Rivers.^[4] At Trenton, New Jersey, the Delaware becomes tidal, navigable, and significantly more industrial. This section forms the backbone of the Delaware Valley metropolitan area, serving the port cities of Philadelphia, Camden, New Jersey, and Wilmington, Delaware. The river flows into Delaware Bay at Liston Point, 48 miles (77 km)^[1] upstream of the bay's outlet to the Atlantic Ocean between Cape May and Cape Henlopen.

Before the arrival of European settlers, the river was the homeland of the Lenape native people. They called the river Lenapewihittuk, or Lenape River, and Kithanne, meaning the largest river in this part of the country.^[5]

In 1609, the river was visited by a Dutch East India Company expedition led by Henry Hudson. Hudson, an English navigator, was hired to find a western route to Cathay (China), but his encounters set the stage for Dutch colonization of North America in the 17th century. Early Dutch and Swedish settlements were established along the lower section of the river and Delaware Bay. Both colonial powers called the river the South River (Zuidrivier), compared to the Hudson River, which was known as the North River. After the English expelled the Dutch and took control of the New Netherland colony in 1664, the river was renamed Delaware after Sir Thomas West, 3rd Baron De La Warr, an English nobleman and the Virginia colony's first royal governor, who defended the colony during the First Anglo-Powhatan War. George Washington's crossing of the Delaware River in 1776 led to the Americans winning the Battle of Trenton, which was a pivotal moment in the American Revolution.

The Delaware River is named in honor of Thomas West, 3rd Baron De La Warr (1577–1618), an English nobleman and the Virginia colony's first royal governor, who defended the colony during the First Anglo-Powhatan War.^[6] Lord de la Warr waged a punitive campaign to subdue the Powhatan after they had killed the colony's council president, John Ratcliffe, and attacked the colony's fledgling settlements.^[7][8] Lord de la Warr arrived with 150 soldiers in time to prevent the colony's original settlers at Jamestown from giving up and returning to England and is credited with saving the Virginia colony.^[6] The name of the barony (later an earldom) is pronounced as in the current spelling form "Delaware" (/ˈdɛləwɛər/ ^ⓘ DEL-ə-wair)^[9] and is thought to derive from French de la Guerre.

It has often been reported that the river and bay received the name "Delaware" after English forces under Richard Nicolls expelled the Dutch and took control of the New Netherland colony in 1664.^[10][11] However, the river and bay were known by the name Delaware as early as 1641.^[12] The state of Delaware was originally part of the William Penn's Pennsylvania colony. In 1682, the Duke of York granted Penn's request for access to the sea and leased him the territory along the western shore of Delaware Bay, which became known as the "Lower Counties on the Delaware".^[13] In 1704, the Lower Counties were given political autonomy to form a separate provincial assembly, but they shared Pennsylvania's provincial governor until the two colonies separated on June 15, 1776, and they remained separate as states after the establishment of the United States.

The name "Delaware" also came to be used as a collective name for the Lenape, a Native American people who inhabited an area of the basins of the Susquehanna River, Delaware River, and lower Hudson River in the northeastern United States at the time of European settlement,^[14] as well as for their language. As a result of disruption following the French and Indian War, American Revolutionary War, and the later Indian removals from the eastern United States, the name "Delaware" has been spread with the Lenape's diaspora to municipalities, counties and other geographical features in the American Midwest and Canada.^[15]

The Delaware River's drainage basin has an area of 13,539 square miles (35,070 km²) and encompasses 42 counties and 838 municipalities in five U.S. states: New York, New Jersey, Pennsylvania, Maryland, and Delaware.^[16]: 9 This total area constitutes approximately 0.4% of the land mass in the United States.^[16]: 9 In 2001, the watershed was 18% agricultural land, 14% developed land, and 68% forested land.^[16]: vi

There are 216 tributary streams and creeks comprising an estimated 14,057 miles of streams and creeks, in the watershed.^{[16]: p.11, 25} While the watershed is home to 4.17 million people according to the 2000 Federal Census, these bodies of water provide drinking water to 17 million people—roughly 6% of the population of the United States.^{[16]: vi, 9} The waters of the Delaware River's basin are used to sustain "fishing, transportation, power, cooling, recreation, and other industrial and residential purposes."^[16]: 9 It is the 33rd largest river in the United States in terms of flow, but is among the nation's most heavily used rivers in daily freight tonnage.^[16]: p.11 The average annual flow rate of the Delaware is 11,700 cubic feet per second at Trenton, New Jersey.^[16]: 9 With no dams or impediments on the river's main stem, the Delaware is one of the few remaining large free-flowing rivers in the United States.^[16]: 11

A 1655 Swedish nautical chart showing part of the Delaware River when the river was part of the Swedish colony New Sweden

• 
  East Branch of the Delaware River near Margaretville, New York
• 
  Canoeing on the river at Hawk's Nest (Orange County, New York)
• 
  A still remaining section of the Delaware and Hudson Canal seen from U.S. 209 near Summitville, New York
• 
  Easton–Phillipsburg Toll Bridge crosses the Delaware, connecting Easton, Pennsylvania and Phillipsburg, New Jersey, in the Lehigh Valley.
• 
  Benjamin Franklin Bridge crosses the Delaware, connecting Philadelphia and Camden, New Jersey.
• 
  Walt Whitman Bridge crosses the Delaware, connecting Philadelphia and Gloucester City, New Jersey.
• 
  Dingman's Ferry Bridge connects Sandyston Township, New Jersey, and Delaware Township in Pike County, Pennsylvania
• 
  The Delaware within the southern portion of the Delaware Water Gap National Recreation Area, near Worthington State Forest in New Jersey
• 
  A flood in Westfall, Pennsylvania, in 2006

The West Branch of the Delaware River, also called the Mohawk Branch, spans approximately 90 miles (140 km) from the northern Catskill Mountains to its confluence with the Delaware River's East Branch at Hancock, New York. The last 6 miles (9.7 km) forms part of the boundary between New York and Pennsylvania.

The West Branch rises in Schoharie County, New York at 1,886 feet (575 m) above sea level, near Mount Jefferson, and flows tortuously through the plateau in a deep trough. The branch flows generally southwest, entering Delaware County and flowing through the towns of Stamford and Delhi. In southwestern Delaware County it flows in an increasingly winding course through the mountains, generally southwest. At Stilesville the West Branch was impounded in the 1960s to form the Cannonsville Reservoir, the westernmost of the reservoirs in the New York City water system. It is the most recently constructed New York City reservoir and began serving the city in 1964. Draining a large watershed of 455 square miles (1,180 km²), the reservoir's capacity is 95.7 billion US gallons (362,000,000 m³). This water flows over halfway through the reservoir to enter the 44-mile (71 km) West Delaware Tunnel in Tompkins, New York. Then it flows through the aqueduct into the Rondout Reservoir, where the water enters the 85 miles (137 km) Delaware Aqueduct, that contributes to roughly 50% of the city's drinking water supply. At Deposit, on the border between Broome and Delaware counties, it turns sharply to the southeast and is paralleled by New York State Route 17. It joins the East Branch at 880 feet (270 m) above sea level at Hancock to form the Delaware.

Similarly, the East Branch begins from a small pond south of Grand Gorge in the town of Roxbury in Delaware County, flowing southwest toward its impoundment by New York City to create the Pepacton Reservoir, the largest reservoir in the New York City water supply system. Its tributaries are the Beaver Kill River and the Willowemoc Creek which enter into the river ten miles (16 km) before the West Branch meets the East Branch. The confluence of the two branches is just south of Hancock.

The East Branch and West Branch of the Delaware River parallel each other, both flowing in a southwesterly direction.

From Hancock, New York, the Delaware flows between the northern Poconos in Pennsylvania, and the lowered shale beds north of the Catskills. The river flows down a broad Appalachian valley, passing Hawk's Nest overlook on the Upper Delaware Scenic Byway. The river flows southeast for 78 miles through rural regions along the New York-Pennsylvania border to Port Jervis and Shawangunk Ridge.

At Port Jervis, New York, it enters the Port Jervis trough. At this point, the Walpack Ridge deflects the Delaware into the Minisink Valley, where it follows the southwest strike of the eroded Marcellus Formation beds along the Pennsylvania–New Jersey state line for 25 miles (40 km) to the end of the ridge at Walpack Bend in the Delaware Water Gap National Recreation Area.^[17][18] The Minisink is a buried valley where the Delaware flows in a bed of glacial till that buried the eroded bedrock during the last glacial period. It then skirts the Kittatinny ridge, which it crosses at the Delaware Water Gap, between nearly vertical walls of sandstone, quartzite, and conglomerate, and then passes through a quiet and charming country of farm and forest, diversified with plateaus and escarpments, until it crosses the Appalachian plain and enters the hills again at Easton, Pennsylvania. From this point it is flanked at intervals by fine hills, and in places by cliffs, of which the finest are the Nockamixon Cliffs, 3 miles (5 km) long and above 200 feet (61 m) high.

The Appalachian Trail, which traverses the ridge of Kittatinny Mountain in New Jersey, and Blue Mountain in Pennsylvania, crosses the Delaware River at the Delaware Water Gap near Columbia, New Jersey.

The Falls of the Delaware at Trenton, where the river becomes tidal. Left - aerial view looking northwest; right - ground view from the New Jersey banks

In Easton, Pennsylvania, the Lehigh River joins the Delaware. At Trenton, the Delaware crosses the Atlantic Seaboard Fall Line with a drop of 8 feet (2.4 m).

Below Trenton, the Delaware flows between Philadelphia and New Jersey before becoming a broad, sluggish inlet of the sea, with many marshes along its side, widening steadily into its great estuary, Delaware Bay.

The Delaware River constitutes the boundary between Delaware and New Jersey. The Delaware–New Jersey border is actually at the easternmost river shoreline within the Twelve-Mile Circle of New Castle, rather than at mid-river, mid-channel or thalweg, so small portions of land lying west of the shoreline, but on the New Jersey side of the river, are pene-exclaves under the jurisdiction of Delaware. The rest of the borders follow a mid-channel approach.

At the time of the arrival of the Europeans in the early 17th century, the area near the Delaware River was inhabited by the Native American Lenape people. They called the Delaware River "Lenape Wihittuck", which means "the rapid stream of the Lenape".^[19] The Delaware River played a key factor in the economic and social development of the Mid-Atlantic region. In the seventeenth century it provided the conduit for colonial settlement by the Dutch (New Netherland) and the Swedish (New Sweden). Beginning in 1664, the region became an English possession as settlement by Quakers established the colonies of Pennsylvania (including present-day Delaware) and West Jersey. In the eighteenth century, cities like Philadelphia, Camden (then Cooper's Ferry), Trenton, Wilmington and New Castle were established upon the Delaware and their continued commercial success into the present day has been dependent on access to the river for trade and power. The river provided the path for the settlement of northeastern Pennsylvania's Lehigh Valley, and northwestern New Jersey by German Palatine immigrants—a population that became key in the agricultural development of the region.

The strategic Delaware River was the scene of several important campaigns during the American Revolutionary War. Perhaps the most famous event was George Washington's crossing of the Delaware River with the Continental Army on the night of December 25–26, 1776, leading to a successful surprise attack and victory against the Hessian troops occupying Trenton, New Jersey, on the morning of December 26.^[20][21]

During the Philadelphia Campaign control of the Delaware River was urgently needed by the British, allowing their naval fleet to supply troops occupying Philadelphia. To this end, the Battle of Red Bank and the Siege of Fort Mifflin were fought on and along the shores of the Delaware by the American and British navies, commanded by Commodore John Hazelwood and Admiral Francis Reynolds respectively.^[22][23][24] See historical map of that campaign.

In 1638, Swedish settlers, led by Peter Menuet, established New Sweden along the Delaware River. This settlement marked one of the earliest European establishments in the region, with Fort Christina (located near modern-day Wilmington, Delaware) becoming a key trading post and symbol of Swedish colonial ambition. The Swedes engaged in peaceful land negotiations with the local Lenape people and developed a thriving colony. New Sweden became a center for trade and cultural exchange between the Swedish settlers, Native Americans, and neighboring Dutch colonies. Although the Dutch would later assert dominance over the region in 1655, New Sweden laid the groundwork for European settlement along the Delaware River. The fort and surrounding settlements played a crucial role in the early European rivalry for control of North America's resources and territory. This era of Swedish colonization is an important part of the Delaware River's history, adding to its diverse cultural legacy.

The magnitude of the commerce of Philadelphia has made the improvements of the river below that port of great importance. Small improvements were attempted by Pennsylvania as early as 1771. Commerce was once important on the upper river, primarily prior to railway competition of 1857.

• The Delaware Division of the Pennsylvania Canal, running parallel with the river from Easton to Bristol, opened in 1830.
• The Delaware and Raritan Canal, which runs along the New Jersey side of the Delaware River from Bulls Island, New Jersey to Trenton, unites the waters of the Delaware and Raritan rivers as it empties the waters of the Delaware River via the canal outlet in New Brunswick. This canal water conduit is still used as a water supply source by the State of New Jersey.
• The Morris Canal (now abandoned and almost completely filled in) and the Delaware and Hudson Canal connected the Delaware and Hudson rivers.
• The Chesapeake and Delaware Canal joins the waters of the Delaware with those of the Chesapeake Bay.

The Delaware Water Gap National Recreation Area came about as a result of the failure of a controversial plan to build a dam on the Delaware River at Tocks Island, just north of the Delaware Water Gap to control water levels for flood control and hydroelectric power generation. The dam would have created a 37-mile (60 km) lake in the center of present park for use as a reservoir. Starting in 1960, the present-day area of the Recreation Area was acquired for the Army Corps of Engineers through eminent domain. Between 3,000 and 5,000 dwellings were demolished, including historical sites, and about 15,000 people were displaced by the project.

Because of massive environmental opposition, dwindling funds, and an unacceptable geological assessment of the dam's safety, the government transferred the property to the National Park Service in 1978. The National Park Service found itself as the caretaker of the previously endangered territory, and with the help of the federal government and surrounding communities, developed recreational facilities and worked to preserve the remaining historical structures.^[25][26]

The nearby Shawnee Inn,^[27][28] was identified in the 1990s as the only resort along the banks of the Delaware River.^[29][30]

American Rivers, an environmental advocacy group, named the Delaware River as the River of the Year for 2020, citing 75 years of progress in reducing pollution and restoring wildlife.^[31]

In 1984, the U.S. Department of the Treasury authorized the creation of a wine region or "American Viticultural Area" called the Central Delaware Valley AVA located in southeastern Pennsylvania and New Jersey. The wine appellation includes 96,000 acres (38,850 ha) surrounding the Delaware River north of Philadelphia and Trenton, New Jersey.^[32] In Pennsylvania, it consists of the territory along the Delaware River in Bucks County; in New Jersey, the AVA spans along the river in Hunterdon County and Mercer County from Titusville, New Jersey, just north of Trenton, northward to Musconetcong Mountain.^[33] As of 2013, there are no New Jersey wineries in the Central Delaware Valley AVA.^[33][34]

In the Project of 1885, the U.S. government undertook systematically the formation of a 26-foot (7.9 m) channel 600 feet (180 m) wide from Philadelphia to deep water in Delaware Bay. The River and Harbor Act of 1899 provided for a 30-foot (9.1 m) channel 600 feet (180 m) wide from Philadelphia to the deep water of the bay.^[35]

Since 1941, the Delaware River Main Channel was maintained at a depth of 40 ft (12 m). There is an effort underway to deepen the 102.5-mile stretch of this federal navigation channel, from Philadelphia and Camden to the mouth of the Delaware Bay to 45 feet.^{[36][37][38][39][40][41]}

The Delaware River port complex refers to the ports and energy facilities along the river in the tri-state PA-NJ-DE Delaware Valley region. They include the Port of Salem, the Port of Wilmington, the Port of Chester, the Port of Paulsboro, the Port of Philadelphia and the Port of Camden. Combined they create one of the largest shipping areas of the United States. In 2015, the ports of Philadelphia, Camden, and Wilmington handled 100 million tons of cargo from 2,243 ship arrivals, and supported 135,000 direct or indirect jobs. The biggest category of imports was fruit, carried by 490 ships, followed by petroleum, and containers, with 410 and 381 ships, respectively. The biggest category of exports was of shipping was containers, with 470 ships.^[42] In 2016, 2,427 ships arrived at Delaware River port facilities. Fruit ships were counted at 577, petroleum at 474, and containerized cargo at 431.^[43]

At one time it was a center for petroleum and chemical products and included facilities such as the Delaware City Refinery, the Dupont Chambers Works, Oceanport Terminal at Claymont, the Marcus Hook Refinery, the Trainer Refinery, the Paulsboro Asphalt Refinery,^[44][45][46] Paulsboro Refinery, Eagle Point Refinery, and Sunoco Fort Mifflin. As of 2011, crude oil was the largest single commodity transported on the Delaware River, accounting for half of all annual cargo tonnage.^[38][47]

The Delaware River is a major barrier to travel between New Jersey and Pennsylvania. Most of the larger bridges are tolled only westbound, and are owned by the Delaware River and Bay Authority, Delaware River Port Authority, Burlington County Bridge Commission or Delaware River Joint Toll Bridge Commission.

After New York City built 15 reservoirs to supply water to the city's growing population, it was unable to obtain permission to build an additional five reservoirs along the Delaware River's tributaries. As a result, in 1928 the city decided to draw water from the Delaware River, putting them in direct conflict with villages and towns across the river in Pennsylvania which were already using the Delaware for their water supply. The two sides eventually took their case to the U.S. Supreme Court, and in 1931, New York City was allowed to draw 440 million US gallons (1,700,000 m³) of water a day from the Delaware and its upstream tributaries.

The Delaware River has been attached to areas of high pollution. The Delaware River in 2012 was named the 5th most polluted river in the United States, explained by PennEnvironment^[48] and Environment New Jersey.^[49] The activist groups claim that there is about 7–10 million pounds of toxic chemicals flowing through the waterways due to dumping by DuPont Chambers Works. PennEnvironment also claims that the pollutants in the river can cause birth defects, infertility among women, and have been linked to cancer.^[48]

In 2015, the EPA saw the Delaware River as a concern for mass pollution especially in the Greater Philadelphia and Chester, Pennsylvania area. The EPA was involved after accusations that the river met standards made illegal by the Clean Water Act. In complying with the Clean Water Act, the EPA involved the Delaware County Regional Water Authority (DELCORA) where they set up a plan to spend around $200 million to help rid the waterway of about 740 million gallons of sewage and pollution. DELCORA was also fined about $1.4 million for allowing the Delaware River to have so much pollution residing in the river in the first place and for not complying with the Clean Water Act.^[50]

Part of the Clean Water Act explains how conditions of the river should be stable enough for human fishing and swimming.^{[citation needed]} Even though the river has had success with the cleanup of pollution, the Delaware River still does not meet that standard of swimmable or fishable conditions in the Philadelphia/Chester region.

In March 2023, a pipe rupture at a Trinseo chemical plant in Bristol, Pennsylvania, released over 8,000 gallons of latex finishing material into the Otter Creek tributary, leading to a water advisory in Philadelphia.^[51]

With the failure of the dam project to come to fruition, the lack of flood control on the river left it vulnerable, and it has experienced a number of serious flooding events as the result of snow melt or rain run-off from heavy rainstorms. Record flooding occurred in August 1955, in the aftermath of the passing of the remnants of two separate hurricanes over the area within less than a week: first Hurricane Connie and then Hurricane Diane, which was, and still is, the wettest tropical cyclone to have hit the northeastern United States. The river gauge at Riegelsville, Pennsylvania recorded an all-time record crest of 38.85 feet (11.84 m) on August 19, 1955.

More recently, moderate to severe flooding has occurred along the river. The same gauge at Riegelsville recorded a peak of 30.95 feet (9.43 m) on September 23, 2004, 34.07 feet (10.38 m) on April 4, 2005, and 33.62 feet (10.25 m) on June 28, 2006, all considerably higher than the flood stage of 22 feet (6.7 m).^[52]

Since the upper Delaware basin has few population centers along its banks, flooding in this area mainly affects natural unpopulated flood plains. Residents in the middle part of the Delaware basin experience flooding, including three major floods in the three years (2004–2006) that have severely damaged their homes and land. The lower part of the Delaware basin from Philadelphia southward to the Delaware Bay is tidal and much wider than portions further north, and is not prone to river-related flooding (although tidal surges can cause minor flooding in this area).

The Delaware River Basin Commission, along with local governments, is working to try to address the issue of flooding along the river. As the past few years have seen a rise in catastrophic floods, most residents of the river basin feel that something must be done. The local governments have worked in association with FEMA to address many of these problems, however, due to insufficient federal funds, progress is slow.^[53]

A number of oil spills have taken place in the Delaware over the years.^[54][55][56]

• January 31, 1975: around 11,172,000 US gallons (42,290 m³) of crude oil spilled from the Corinthos tanker
• September 28, 1985: 435,000 US gallons (1,650 m³) of crude oil spilled from the Grand Eagle tanker after running aground on Marcus Hook Bar
• June 24, 1989: 306,000 US gallons (1,160 m³) of crude oil spilled from the Presidente Rivera tanker after running aground on Claymont Shoal
• November 26, 2004: 265,000 US gallons (1,000 m³) of crude oil spilled from the Athos 1 tanker; the tanker's hull had been punctured by a submerged, discarded anchor at the Port of Paulsboro. In 2020, the Supreme Court ruled that Citgo had failed to provide a safe berth for the vessel and was therefore jointly responsible for clean up costs. The company was ordered to pay $143 million.

The National Marine Fisheries Service is considering designating sixteen rivers as endangered habitat for the Atlantic sturgeon which would require more attention to be given to uses of the rivers that affect the fish.^[57]

The river is part of the National Wild and Scenic Rivers System.

• Foul Rift, rapids just south of Belvidere, New Jersey
• Geography of Pennsylvania
• List of municipalities on the Delaware River
• List of crossings of the Delaware River
• List of rivers of Delaware
• List of rivers of New Jersey
• List of rivers of New York
• List of rivers of Pennsylvania
• List of most-polluted rivers
• Partnership for the Delaware Estuary
• Upper Delaware Scenic and Recreational River

• Brooks, Victor (1999). How America Fought Its Wars. New York: Da Capo Press. ISBN 1-58097-002-8.
• Devastation on the Delaware: Stories and Images of the Deadly Flood of 1955 Archived May 14, 2021, at the Wayback Machine (2005, Word Forge Books Archived April 18, 2021, at the Wayback Machine, Ferndale, PA) The only comprehensive documentary of this weather disaster in the Delaware River Valley.
• Leach, Josiah Granville (1902). "Commodore John Hazlewood, Commander of the Pennsylvania Navy in the Revolution". The Pennsylvania Magazine of History and Biography. 26 (1). The Historical Society of Pennsylvania: 1–6. JSTOR 20086007.
• McGeorge, Wallace (1905). The Battle of Red Bank, Resulting in the Defeat of the Hessians and the Destruction of the British Frigate Augusta, Oct. 22 and 23, 1777. Camden, New Jersey: Sinnickson Chew, Printers.
• Savas, Theodore (2006). Guide to the Battles of the American Revolution. Savas Beatie. ISBN 1-932714-12-X.

Wikimedia Commons has media related to Delaware River.

• Delaware Riverkeeper Network
• Delaware River Basin Commission
• Delaware River Vessel Reporting System
• National Park Service: Delaware Water Gap National Recreation Area
• National Park Service: Upper Delaware Scenic & Recreational River
• National Park Service: Lower Delaware Wild & Scenic River
• U.S. Geological Survey: NJ stream gaging stations
• U.S. Geological Survey: NY stream gaging stations
• U.S. Geological Survey: PA stream gaging stations
• Early Americas Digital Archive

• Marine Railway and Sectional Floating Dry Dock, Delaware River, Philadelphia, 1893 by D.J. Kennedy, Historical Society of Pennsylvania Archived November 19, 2012, at the Wayback Machine
• Winter on the River Delaware, 1856. Shows "U.S.S. Powhatan" by D.J. Kennedy, HSP Archived May 7, 2012, at the Wayback Machine
• "Map of the South River in New Netherland" from c. 1639 via the World Digital Library
• Socioeconomic Value of the Delaware River Basin in Delaware, New Jersey, New York, and Pennsylvania

• "Delaware, a river of the United States" . Collier's New Encyclopedia. 1921.
• "Delaware River" . The New Student's Reference Work . 1914.
• "Delaware. A river of the Eastern United States" . New International Encyclopedia. 1905.