U.S. Federal Route 51 is a north-south highway in Central La Salle County. It runs competely on the Interstate 39 expressway. This crosses the Illinois River on the Abraham Lincoln Memorial Bridge. At La Salle-Peru there are two former alignments. One is designated Illinois State Route 251, and the other Illinois State Route 351. U.S. Rt. 51 does not pass through any towns in La Salle County. U.S. Rt. 51 is multi-plexed in La Salle County. Interstate 39, throughout La Salle County.