(Cahokia Mounds State Historical Site) W. of Collinsville, IL. Collinsville Rd. W. 1.5 miles from jct with I255 exit 24 W. of Collinsville, S. on 0.25 miles to the cake on the W. side of the road. (N38 39.300 W90 03.542) Photos by Jack & June Schmidt 4-6-14.