The western terminus of SR 185 is at U.S. Route 127 (US 127) approximately 3.75 miles (6.04 km) south of North Star.

The original highway system was designed to promote economic growth and provide better access to goods and services for Ohio's residents.

In the 1970s, concerns about safety on Ohio State Route 185 began to arise due to its intersections with other major roads.

[4][5] By 1953, when US 127 was re-routed onto a more direct alignment in northern Darke County, SR 185 was extended a short distance west to its current western terminus at the then newly-realigned US 127.

The new route turns south onto the newly constructed Progress Way before joining SR 47 on Greenlawn Avenue.