State Route 173 is located in northeastern Ohio, and runs east–west from State Route 44, about 4 miles (6.4 km) north of Louisville, Ohio to State Route 14 and State Route 9 in downtown Salem, Ohio. It primarily passes through Stark and Columbiana counties, though it also straddles the county line between Mahoning County and Columbiana County for some of its length. Much of the route is also ran in concurrency with U.S. Route 62.