This is the Chicago and North Western Railroad swing bridge over the Missouri River between South Dakota's capital city of Pierre and its companion city of Fort Pierre. Completed in 1907, it served until service was discontinued in 1986. The second span from the east (Pierre) end of the bridge is a swing span that rotated open to allow passage to high-clearance boats. It no longer functions. Nor, in practicality, does the bridge, which (as of 2021) remains the only swing bridge standing in South Dakota. Photo by Carol Highsmith, 2021.