After 1940, a series of lock and dams were in place in the Mississippi River between Minneapolis and Alton. These facilitated barge traffic in this region. There remained a short segment of the River north and east of Saint Louis with limited navigation due to rock ledges and shelves.
To solve this problem, the Army Corps of Engineers proposed an 8.4 mile canal to bypass this area. The canal runs from just south of the mouth of the Missouri River to just north of downtown Saint Louis. The area of the canal is in a region where bedrock is close to the surface. The canal could only be dug to a limited depth. To solve this limitation, a dam was built in the Mississippi River just south of the entrance of the canal. This allowed for an extra 3 feet of depth in the Chain of Rocks Canal.