The southern terminus of SR 308 is at SR 229 in the western end of the village of Gambier, and its northern terminus is three miles (4.8 km) to the north of that point at a T-intersection with U.S. Route 36 (US 36) that is located approximately one and a half miles (2.4 km) east of the city limits of Mount Vernon.

SR 308 runs exclusively in the central portion of Knox County.

The route is not a part of the National Highway System.

[2] When first designated in 1932, SR 308 was a spur route connecting US 36 with the village of Gambier and Kenyon College.

[5][6] The entire route is in Knox County.