9.2 miles in length, SR 66 acts as a connector between SR 28 at the settlement of Consul and SR 5 near the unincorporated community of Safford. SR 66 forms part of a regional route between the Marengo County seat of Linden and the Dallas County seat of Selma.
East
SR 66 eastbound concludes at SR 5 in rural Dallas County. SR 5 connects with SR 22 east at Safford in 1.25 miles.