Ohio State Route 177 runs northwesterly out of Hamilton to the Indiana border. At the state line, it becomes Indiana State Route 227, bound for Richmond, Indiana. The southeastern point of beginning is on the west side of Hamilton, where Main Street meets Eaton Avenue and Millville Avenue. As Main Street progresses northwestward out of downtown, Ohio Route 129 turns left from Main Street onto the westward Millville Avenue. Ohio Route 177 begins in the wake of Ohio Route 129 to continue northwest on Main Street. Beyond Hamilton, Ohio Route 177 runs northwesterly, sandwiched between US Route 27 and US Route 127. It flanks the eastern side of Oxford, passing through Darrtown instead. Ohio Route 177 joins Ohio Route 732 north for a bit near Hueston Woods State Park. Then it splits and heads for the Indiana border, where it ends.