Marengo County is a county in the U.S. state of Alabama. As of the 2010 census, the population was 21,027. The largest city is Demopolis and the county seat is Linden. It is named in honor of the site of Battle of Marengo near Turin, Italy, where French leader Napoleon Bonaparte defeated the Austrians on June 14, 1800.
Marengo County was founded on February 6, 1818.