The Old Plank Road Trail is a 21-mile (34 km) long public rail trail in Cook County and Will County within the U.S. state of Illinois. It stretches westward from Chicago Heights (41°29′56.5″N 87°39′4.6″W / 41.499028°N 87.651278°W) to Joliet (41°31′23.6″N 88°3′16.0″W / 41.523222°N 88.054444°W), serving fast-growing suburbs such as Frankfort and New Lenox.