The first attempt to solve the navigation problem involved building a canal and lock around the worst of the rapids upstream near the present day Lock & Dam #14. That was built for the 6-foot navigation project. While a modern dam with 9-foot locks have been built at that site, the canal and 6-foot lock is still in use for pleasure craft.
After World War I, technology lead to larger river boats that required a deeper draft. Congress funded the 9-foot navigation project. This project required that the Le Claire lock and dam be upgraded from a 6-foot structure to a 9-foot structure. At the same time, a second 9-foot structure would be required only a few miles downstream. The site that was picked was between Davenport and Rock Island, at the foot of Arsenal Island. Construction was tricky because the double deck Government rail and road bridge crossed the site. In fact, that bridge had a swing section to allow river traffic to pass. That swing section was located between the two locks, and would swing to be parallel with the center wall between the locks. This allowed both locks to be clear for traffic to enter and exit while the swing span was open.
The dam is built with 11 gates. The gates are hollow metal tubes that can be lowered into the water to block the river flow. Each gate is 109 feet wide. This is reported to be the largest dam in the world made exclusively from roller gates. These roller gates were new technology in the late 1920s. In fact, the US Army stole the technology from Germany after WWI. Most other locks and dams on the great river use a combination of roller gates and Tainter gates.