Florida State Road 121

SR 121 is one of the major routes of a three-state highway 121 that totals approximately 475 miles (764 km) from Lebanon Station, Florida, to Rock Hill, South Carolina.

Beginning in Lebanon Station at a channelized intersection with US 19/US 98 and County Road 336 (CR 336) in Levy County, SR 121 travels through Goethe State Forest where it turns east and intersects CR 337. The road makes a sharp left curve to the northeast where it travels through desolate farmland; the only resemblance to a major intersection is CR 326. Within the city of Williston, SR 121 has a concurrency with CR 316, until the intersection with US 41. It then joins US 41 as CR 316 continues eastward, which then joins the east end of US 27 Alternate (US 27 Alt.), and then the US 27/US 41 concurrency before breaking away to the northeast again, taking the DeSoto Trail away from US 41.

North of CR 335, SR 121 hugs the west side of the Levy–Marion county line, but never crosses it, choosing to enter Alachua County instead. Immediately after the interchange with Interstate 75 (I-75) at exit 382, SR 121 makes a sharp left onto Northwest 34th Street as SR 331 becomes the designation for Williston Road. As it crosses SR 24 it borders the western edge of the University of Florida, passing along the 34th Street Wall just before crossing SR 26A and then SR 26. North of US 441, the DeSoto Trail breaks away.

Within the town of LaCrosse, SR 121 shares a short concurrency with SR 235, then has a level crossing with the CSX Brooker Subdivision, a former Seaboard Coast Line railroad line that leads to the Crystal River 3 Nuclear Power Plant. After the intersection with CR 236 in Santa Fe, SR 121 passes by entrances to the Santa Fe River Preserve, and then is carried along a bridge over the Santa Fe River in Worthington Springs, where it intersects SR 18. North of CR 18, the road is carried along a bridge over the former Jacksonville and Southwestern Railroad.

Briefly traveling parallel to SR 100 in Lake Butler, it intersects SR 100 as it continues northeast. The road also intersects SR 16 in Raiford, and I-10 (Exit 335) and US 90 in Macclenny close to SR 228 before crossing the Georgia state line on its way to South Carolina.

The segment between US 19 and 98 in Lebanon Station and US 41 in Williston was previously designated as Florida State Road 335, and the segment between US 27 and 41 in Williston, at what is today the south end of SR 331 was part of a southern extension of that route.[2]
State Road 23 was defined in the 1945 renumbering as:

• From a point on SR 20 and SR 25 approximately 1 mile (1.6 km) northwest of Paradise in a northwesterly direction to the intersection with SR 235 in LaCrosse and along SR 235 for approximately 0.07 miles (0.11 km), then continuing northwesterly via Santa Fe to a junction with SR 18 at Worthington Springs and along SR 18 to a point approximately 1 mile (1.6 km) north of Worthington Springs, then northeasterly to a junction with SR 100 in Lake Butler and East on SR 100 to a point near the eastern city limits of Lake Butler then northeasterly via Raiford to a junction with SR 10 in Macclenny and along SR 10 to 5th Street then in a northerly direction along 5th Street to the St. Mary's River at the Georgia state line.

Prior to the renumbering, this had been:

• SR 99 from northwest of Paradise to Worthington Springs
• SR 113 from northwest of Paradise to LaCrosse
• SR 49 from Worthington Springs to Georgia

At some point, SR 23 was renumbered as part of SR 121, probably to match Georgia State Route 121. Before that, however, SR 23 had been extended around the west side of Gainesville to end at US 441/SR 25 at Rocky Point, and the southernmost part did not become part of SR 121. It was later given to the county, and has a possibility of becoming County Road 23.

The State Road 23 designation has since been reused for a partial beltway around Jacksonville.

In 1975, the City of Gainesville recommended a truck ban along SR 121 and established a truck route around downtown. In 1979. FDOT widened the road within the city, which included the creation of a retaining wall along the University of Florida Golf Course that has since become a target for graffiti artists. The truck ban was lifted in the early 1980s, but reestablished later in the decade after a series of fatal accidents.