One of the largest river-development programs in U.S. history, the Nine-Foot Channel Project turned the often unnavigable Upper Mississippi into a smooth-flowing riverine highway. Dams regulate the water level, creating a 669-mile chain of slack-water navigation pools, each at least nine feet deep. Locks lift or lower vessels from one pool to the next. The U.S. Army Corps of Engineers conceived the project in the 1920s to forge a transportation link between north and south, ideally alleviating inequities in rail and water-freight rates. By the time construction began during the Great Depression, the Corps recast it as a massive New Deal employment project.
Each lock-and-dam complex includes a set of locks, a movable dam, whose gates can be opened to release water and debris, and outbuildings such as control stations and employee housing. Three types of dam gates were used: cylindrical submersible and nonsubmersible roller gates and Tainter gates. Submersible roller gates can roll three feet below the surface to allow ice, debris, or floodwater to pass overhead. Formerly, nonsubmersible roller gates, which rose to allow debris and water to pass underneath, caused serious riverbed erosion. Tainter gates are shaped like a long section of a cylinder, with the convex side facing upstream. The gate rises or falls by pivoting on wedge-shaped rocker arms attached to it at either end. Lock and Dam No. 7 features all three types. The 940-foot movable dam is supplemented by a 670-foot fixed dam and a 9,003-foot earthen dike along the northwest shore of French Island, which separates the Black River from the Mississippi. Chicago’s Warner Construction Company served as the general contractor for Dam No. 7, and Bethlehem Steel fabricated the gates. Nolan Brothers and the Minneapolis Dredging Company (both of Minneapolis) and the Dearborn Electrical Construction Company (Chicago) built the locks.
The earliest Nine-Foot Channel Project dams were utilitarian in design, but those built in the late 1930s were Moderne (see BF3) in style, popular for New Deal public works. This one features slit-shaped windows. The control building, however, is Georgian Revival, with hipped roofs, pilasters, and paired arched windows. The style connoted the heritage and authority of early Anglo-Americans and became an all-American mode in the 1920s and 1930s. The connotation of authority may have made it seem right for a control building.