Illinois Route 157 is mainly a north-south route in the Metro-East, with a small "J"-shaped hook at the southern end. The northern end is in the small town of Hamel at Illinois 140, just seconds west of Interstate 55. It heads south-southwesterly overall, passing through Edwardsville, Collinsville, Caseyville, and Centreville. At Centreville, Illinois 157 bends northwesterly to form the hook of the "J"-shape. The end of the hook, and the end of the route, is at Illinois 3 in Cahokia Heights.