It runs for 39.9 miles (64.2 km)[1] from Carter, Oklahoma to the unincorporated community of Lake Valley.

SH-55 begins at State Highway 34 in Carter, in eastern Beckham Co.

It heads east for six miles (10 km), where it meets State Highway 6 and overlaps it to the south.

After running along the Beckham/Washita Co. line, it splits off to the east near Retrop.

It then terminates at State Highway 54 in Lake Valley.