Its eastern terminus is at an intersection with US 23 and SR 317 approximately 2.50 miles (4.02 km) northwest of the village of Lockbourne.

There is no segment of this route that is included within the National Highway System, a system of highways deemed most important for the nation's economy, mobility and defense.

[2][3] Just two years later, the highway was extended on the east end, via a short jog northerly along US 23, then east along what is today SR 317 from US 23 into Groveport, where the route came to an end at the Main Street intersection.

[5][6] Then, in 1973, a southward extension of SR 317 through the eastern portion of suburban Columbus resulted in that highway being extended to Groveport.

Consequently, SR 665 was restored to its original routing, and has not changed since that time.