Route 173 follows the Chaudière River for most of its course, from Saint-Georges, down to Scott, where the route takes a more northeastern route towards Lévis, crossing the Etchemin River in the municipality of Saint-Henri-de-Lévis.
Following the Chaudière River, Route 173 extends from Saint-Georges to Scott. It then heads northeast toward Lévis and crosses the Etchemin River within the municipality of Saint-Henri-de-Lévis.