There are 10 US Post Offices in Marengo County serving a total of 20,201 residents equating to 2,020 residents per post office. It's estimated that approximately 32,243 packages are handled across the 10 county post offices annually. Marengo County is a county of 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 battlefield of the site of Battle of Marengo near Turin, Italy, where the Napoleon Bonaparte defeated the Austrians on June 14, 1800."