Lake Jefferson, located in Le Sueur, Minnesota, is a state-owned reservoir with a primary purpose classified as "Other." Built in 1938 by WPA-BC, this gravity dam stands at a height of 7.25 feet and a length of 15 feet. With a normal storage capacity of 18,544 acre-feet and a maximum storage of 25,489 acre-feet, Lake Jefferson covers a surface area of 700 acres and serves a drainage area of 16.3 square miles. The dam's hazard potential is rated as low, and its condition assessment is deemed satisfactory as of 2009.

Situated in the city of Waterville, Lake Jefferson is fed by the Big Cannon River and falls under the jurisdiction of the St. Paul District of the US Army Corps of Engineers. Despite not being regulated by the state or requiring inspections, the dam remains an integral part of the area's water resource management system. With its historical significance as a Works Progress Administration project, Lake Jefferson continues to provide essential water storage and recreational opportunities for residents and visitors alike. The dam's low hazard potential and satisfactory condition underscore its importance in ensuring water security and climate resilience in the region.