File:Upper St. Anthony Falls Dam, Mill District, Minneapolis, MN - 51781555290.jpg

English: Built between 1952 and 1963, this concrete dam was built to prevent the further erosion of the limestone layer beneath Saint Anthony Falls and the natural process that would have led to the falls becoming a series of rapids useless for hydropower purposes, a process which had accelerated due to industrial development around the falls in the late 19th Century, leading to the construction of the first dam in the 1850s, and the installation of a timber apron over the falls in 1870. The timber apron was maintained until 1952, when a major flood heavily damaged it, prompting the construction of a more permanent and durable concrete apron over the falls, as well as the present dam and lock structure to allow for navigation upstream of the falls. The dam stands 14 feet high over the 35-foot falls, increasing the total vertical drop to 49 feet.