It runs east–west for approximately ten miles (16 km) between two intersections with U.S. Route 20 (US 20) west of Vale and in the city.

The OR 451 designation was established in 2003 as part of Oregon's project to assign route numbers to existing named highways that previously were not assigned.

Highway 451 begins at a junction with US 20 at its crossing of the Malheur River southwest of Vale.

The highway travels northwest on Canyon Road, briefly turning west and then north again, to reach Graham Boulevard.

Highway 451 then turns east and continues into Vale, where it terminates at another junction with US 20.