Black Hawk County was created in 1843 and named for the Sac war leader who lost the war that bears his name. It is in the eastern part of the state and is bounded by Bremer, Buchanan, Benton, Tama, Grundy, and Butler counties. The present land area is 567 square miles, and the population in 2000 was 128,012. The county seat is Waterloo.