Federal Dam is a city in Cass County, Minnesota, United States, near Leech Lake. The population was 123 at the 2020 census. It is part of …Federal Dam is a city in Cass County, Minnesota, United States, near Leech Lake. The population was 123 at the 2020 census. It is part of the Brainerd Micropolitan Statistical Area. A post office called Federal Dam was established in 1910. The city took its name from a nearby dam constructed by the federal government of the United States.