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.
NB I-39/U.S. Rt. 51 at the La Salle/Marshall County Line. NB I-39/U.S. Rt. 51 north of IL St Rt 18. NB I-39/U.S. Rt. 51 near Lostant. SB I-39/U.S. Rt. 51 south of Tonica. NB I-39/U.S. Rt. 51 near Tonica. SB I-39/U.S. Rt. 51 south of Oglesby. A set of guide markers on EB U.S. Rt. 6. A set of BGS's on WB I-80. A BGS on WB I-80. NB I-39/U.S. Rt. 51 north of La Salle. NB I-39/U.S. Rt. 51 north of I-80. SB I-39/U.S. Rt. 51 south of U.S. Rt. 52. A junction marker on EB U.S. Rt. 52. A junction marker on EB U.S. Rt. 52. A BGS on EB U.S. Rt. 52. A guide marker on EB U.S. Rt. 52. A BGS on EB U.S. Rt. 52. NB I-39/U.S. Rt. 51 north of U.S. Rt. 52. SB I-39/U.S. Rt. 51 south of U.S. Rt. 34. A guide marker on EB U.S. Rt. 52/SB IL St Rt 251. NB I-39/U.S. Rt. 51 north of U.S. Rt. 34. SB I-39/U.S. Rt. 51 at the La Salle/Lee County Line.
