Locks and Dam 15 was the first project completed on the Upper Mississippi River as part of an overall project to create a nine-foot navigation channel. It was built to control water levels through the Rock Island Rapids from Rock Island, Illinois, to LeClaire, Iowa, and provide consistent river depths. This was considered one of the most dangerous areas on the river. Part of the rocky material creating the rapids was removed from the river and the dam submerged the rest. This improved navigation on the river. The lock began operation in August 1933.From the U.S. Army Corps of EngineersIn the heart of the Quad Cities, Locks and Dam 15 is 483 miles above the confluence of the Mississippi and Ohio rivers. The complex stretches across the Mississippi River at one of its narrowest points at the foot of the Rock Island Rapids, extending from the northwest tip of Arsenal Island on the Illinois side to a small area of flat-bottom land on the Iowa side. A roadway and railroad bridge, joining Davenport and Rock Island, spans the site.The complex was the first completed in the 9-Foot Channel Project and served as a prototype for the whole system. Dam 15 is unusual as it is the only one on the river made entirely of roller gates. It was constructed at the narrowest part of the channel and is subject to ice and debris jams. It is built at a 16-1/2 degree angle to gain additional dam area for maintaining the navigation channel; it employs roller gates that are non-submersible, of differing sizes, and of non-standard length; it is not at a right angle to the river; it includes no earthen embankment dike section; it incorporates a power plant that generates electricity to operate its gates and valves; and it uses an open-truss service bridge with a bulkhead-lifting crane on its lower chord. The complex is also unusual because the intermediate locks' wall encases a bridge swing span.The contractor for the lock construction was favored with low river stages, a mild winter in 1931-1932, and satisfactory labor conditions. The average number of employees during construction was 221.The lock and dam elements of the complex were completed at a cost of $7.48 million.Locks and Dam 15 FactsConstruction: Began April 1931 Completed: December 1932 -- Locks. May 1934 -- Dam Fully Functional: March 7, 1934 Length: 1,203 feet Height: 78 feet Roller Length: 99.3 feet Rollers: 11 Average Water Flow: 377,740 gal/sec Average Tonnage of Cargo Passing Through: 21,765,385