La Salle County Highway 51 is a alternative to U.S. Rt. 6 for a journey between Marseilles and Ottawa. Also, this provides access to the GE Plastics Plant between the two towns. LSCH 51 passes through the following towns in La Salle County. Ottawa Marseilles LSCH 51 intersects the following major local roads in La Salle County. U.S. Rt. 6, at Ottawa. Illinois State Route 71, at Ottawa.