The City of Fort Atkinson is a vibrant community located along the Rock River, a few miles upstream from Lake Koshkonong, in Jefferson County. Fort Atkinson is the largest city located entirely in the county. The city developed at the former site of Fort Koshkonong which was used during the 1832 Black Hawk War. Fort Atkinson’s name is derived from the original fort and General Henry Atkinson, who was in charge of the US forces during the war.