Lock and Dam No. 12 is a lock and dam located on the Upper Mississippi River at Bellevue, Iowa, United States. The movable portion of the dam starts at the locks adjacent to the Iowa shore and is 849 ft long, consisting of seven tainter gates and three roller gates. It connects to a 200 ft storage yard and continues toward the Illinois shore with a 2750 ft non-submersible dike, a 1200 ft submersible dike and a 3130 ft non-submersible dike. The non-submersible sections are separated from the submersible section with two 120 ft transitional dikes. The main lock is 110 ft wide by 600 ft long. There is also an incomplete auxiliary lock. In 2004, the facility was listed in the National Register of Historic Places as Lock and Dam No. 12 Historic District, #04000172 covering 1017 acre, 1 building, 3 structures, and 4 objects.