Lock and Dam No. 8 is a lock and dam located near Genoa, Wisconsin on the Upper Mississippi River near river mile 679.2 in the United States. It was constructed and was put into operation by April 1937. The site underwent major rehabilitation from 1989 to 2003. The lock and dam are owned and operated by the St. Paul District of the United States Army Corps of Engineers-Mississippi Valley Division. The dam consists of a concrete structure 934 ft long with five roller gates and 10 tainter gates. The earth embankment is 17500 ft long with two submersible spillways, 938 ft long and 1338 ft long. The lock is 110 ft wide by 600 ft long.