The longest interstate highway in Tennessee is Interstate 40, at a length of 454.81 miles (731.95 km). The segment of I-40 in Tennessee is also the longest segment of all of the states the route traverses. The shortest mainline interstate highway in Tennessee is I-55, at a length of 12.28 miles (19.76 km) in Memphis. The longest auxiliary interstate highway in Tennessee is I-840, an outer southern bypass around Nashville, at a length of 77.28 miles (124.37 km). The shortest interstate highway in Tennessee is the 1.97 miles (3.17 km) I-124 in Chattanooga, which is unsigned; the shortest signed interstate highway is I-275 in Knoxville, at 2.98 miles (4.80 km) long.
History
Tennessee was allocated approximately 1,047.6 miles (1,685.9 km) of Interstate Highways by the Federal Aid Highway Act of 1956.[4] I-24 was originally planned to run between Nashville and Chattanooga; it was approved to be extended to I-57 in southern Illinois in August 1964.[5]
The first section of Interstate Highway in Tennessee was a short freeway in Knoxville, completed in two segments in 1952 and 1955, that was integrated into the Interstate Highway System, becoming part of I-40 and I-75.[6][7][8] The first initial segment of Interstate Highway in Tennessee was a short portion of I-65 near the Alabama state line that opened on November 15, 1958.[3]
The first section of Interstate to be complete between two major cities in Tennessee was I-40 between Memphis and Nashville, the last segment between these cities of which was dedicated on July 24, 1966.[9][10] Most of I-40 between Nashville and Knoxville was also complete by this time. On December 20, 1974, the final segments of I-40, I-75, and I-81 in Tennessee opened to traffic, opening the final segments of mainline Interstate Highway initially allocated to Tennessee in 1956.[11][12] At this time, however, work was not fully complete on these sections of I-81 and I-40; this occurred on August 27, 1975[13] and September 12, 1975, respectively.[14] The last segment of I-24 in Tennessee, located west of Nashville, opened on January 5, 1978.[15][16] The last segment of Interstate Highway in Tennessee to be completed that was planned by the Interstate Highway Act was on I-440 in Nashville, which opened on April 3, 1987.[17]
Due to citizen opposition, a short segment of I-40 in Memphis planned to pass through the city's Overton Park was never built. Opposition began after the routing was proposed in the 1950s, and citizens waged a multi-year legal battle that culminated in the U.S. Supreme Court case Citizens to Preserve Overton Park v. Volpe in 1971.[18] After this case, TDOT continued to explore options to construct this section until 1981, when it was abandoned, and a nearby section of I-240 was redesignated as part of I-40.[19]
Since the completion of Tennessee's original Interstates, additional segments of highway in the state have been added to the system. An extension of I-26 into Tennessee was approved by AASHTO in 1988, and officially incorporated in August 2003.[20] I-140 is a designation that was applied to a section of the Pellissippi Parkway in Knox and Blount counties that was constructed in the 1990s. I-840 was first proposed by the state legislature in 1986 and constructed between 1991 and 2012;[21] it officially became an Interstate Highway on August 12, 2016.[22] A segment of SR 385 in the Memphis area became I-269 in 2018.
An extension of I-69 into Tennessee was proposed in the 1990s. In 2005, I-3 was also proposed into Tennessee as a Third Infantry Division Highway.
Entire loop at one time proposed to be I-240. Northern side of loop designated as I-40 upon completion, due to abandonment of plans to build I-40 through Overton Park.
Proposed I-75 bypass of Knoxville, also proposed to be extended to I-40 at exit 407 (SR 66) to provide a complete northern beltway of Knoxville and provide a more direct route to Sevier County/Great Smoky Mountains National Park
^Special Committee on U.S. Route Numbering (June 7, 1988). "Route Numbering Committee Agenda"(PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. p. 4. Retrieved November 11, 2015 – via Wikimedia Commons.
^Tennessee Department of Transportation (2012). State Route 840: Enjoy the Ride(PDF) (Dedication program). Tennessee Department of Transportation. Archived from the original(PDF) on November 19, 2012. Retrieved June 12, 2015.