In the early 1950s, FDOT acquired part of the Kissimmee Valley Line of the Florida East Coast Railway in Orange and Seminole Counties for highway purposes.

It passes through central Lake Mary and overlaps CR 46A in western Sanford.

The 1945 definition of SR 15 included an alternate route bypassing Sanford to the west, from north of Longwood to just south of the St. Johns River.

[4] However, no road was ever built south of CR 427, and maps indicate that a portion in northern Lake Mary was not state maintained.

County Road 46A begins at the south end of CR 431 (Orange Boulevard) near Paola and runs east on H.E.

SR 46A was not part of the original 1945 plans, but it was added to the state highway system by the 1950s.

Road signage properly shows west 46A ends at the intersection of H. E. Thomas Parkway and Orange Blvd.

The route began at SR 426 and followed the entire length of Tuskawilla Road (now inventoried as CR 4281).

County Road 427 follows Maitland Avenue and Ronald Reagan Boulevard along the old Dixie Highway from the Orange County line to the south end of CR 425 (Sanford Avenue) just north of Lake Mary Boulevard.

(However, a short piece in southern Longwood was part of the original route of SR 434, from North Street (where Anchor Road formerly connected) to Warren Avenue.)

County Road 431 is signed on Orange Boulevard through Paola, extending north from CR 46A.

No signs are posted elsewhere along the route, but FDOT GIS data indicates that the north end is at SR 46.

In 1980 it became a county road, and now extends on former SR 46A to the south end of Orange Boulevard.