The US Army Corps of Engineers started the project by building a 2.7 mile long canal just to the south of the Illinois River to bypass the rapids. A dam was built across the river at the upstream end of the canal. The locks were were built here at the downstream end of the canal. This allowed the dam to keep the water high in the canal, and the canal to bypass the rapids.
The lock at this location is the same size as the other four locks on the Illinois River, the 110 foot wide by 600 foot long Panama Canal standard size lock. While the Panama Canal locks were big when built, today, they are small compared with the size of barge tow that often uses the river. In fact, many tows have to be broken up into two pieces to lock through, and then are reassembled after the second piece exists the lock. This takes time and dramatically reduces the traffic level that the lock can maintain.
The Marseilles Lock can be accessed from the Illini State Park on the south side of the river, and then following the park service road to the west. There is a parking area and observation plaza for the public to watch the lock in operation. A large iron fence has been erected, but the bars are far enough apart to slide your camera between the bars and take photos.
