West of Worthington Springs, County Road 18 is a bi-county road that extends from US 27 (SR 20) in Fort White as County Road 18, also known as Southwest Fellowship Street along the O'Leno to Ichetucknee Trail.[2] The road takes a slight curve to the northeast that ends near the intersection of County Road 131 just south of that road's own intersection with CR 238. At the west end of the short concurrency with US 41/441 (SR 25) in Mikesville, CR 18 turns north, while the trail turns south towards O'Leno State Park. Once the concurrency ends, CR 18 turns east again at the intersection of Hammock Road, and becomes Southeast Sebring Street.
Though the road isn't necessarily straight, CR 18 still runs relatively east and west, including when it uses a bridge over Interstate 75 with no access. Later on, it crosses the Columbia-Union County line at a bridge over Olustee Creek, and becomes County Road 18. Along this segment are semi-notable intersections such as CR 791, and then CR 241 which runs through three other counties. Later it serves as the southern terminus of both CR 239 and then CR 238A. The road just enters northern Worthington Springs, Florida at the intersection with State Road 121, then follows that route south in a hidden concurrency with the state road it was originally part of.
County Road 18A is the one suffixed alternate route of SR 18. It begins at SR 18 east of the Worthington Springs town limits and heads north, around the west and north side of a local airport named Flying Tiger Field, although on the north side of this airport it runs northeast and southwest. Before the intersection with Southwest 131st Lane the route turns east and then curves to the north at the two intersections with Southwest 142nd Place. It takes a curve to the northwest after a dead end street named Southwest 53rd Terrace, but take a far more drastic turn west at the intersection of Southwest 63rd Street, a connecting route to CR 231A. CR 18A ends at SR 121 across from the eastern terminus of CR 239A.
County Road 18 is the other county extension of SR 18. It begins at CR 231/CR 235 in Brooker and runs east along the north side of the Santa Fe River. Leaving the town limits, it eventually approaches an intersection with County Road 231 which runs closer to the county line in a half loop, and is not the same CR 231 that is overlapped by CR 235. After the east end of the CR 231 loop, the road enters Graham where it serves as the northern terminus of CR 225 then curves to the northeast until it branches off to the east again, and CR 227 serves as the replacement route for the same road.
The surroundings of the route are primarily wooded with occasional breaks of private property, but then runs along the northeast shore of Hampton Lake. Once it leaves the vicinity of the lake, County Road 18 is named Navarre Avenue and then has a major intersection with US 301 in Hampton. Within that city, CR 18 has a concurrency with CR 221, and then has an at-grade crossing with the CSX Wildwood Subdivision, which is part of the S-Line, and carried Amtrak's Silver Star/Palmetto line until November 2004. Later, it has an intersection with the northern terminus of CR 325, just before CR 221 veers off to the left, heading northeast back to US 301. Leaving Hampton, the route turns southeast and will keep this trajectory until it seems to terminate at SR 100 near Theressa. However CR 18 secretly runs south along a concurrency with SR 100 until it reaches Southeast Ninth Avenue, veering straight and later turning onto Southeast Second Place which leads to Crystal Lake on the Alachua-Clay County line where the route ends.
