[1] It is named in honor of the Battle of Marengo near Turin, Italy, where French leader Napoleon Bonaparte defeated the Austrians on June 14, 1800.

Marengo County was created by the Alabama Territorial legislature on February 6, 1818, from land acquired from the Choctaw by the Treaty of Fort St. Stephens on October 24, 1816.

[3] Like the other four of the "Five Civilized Tribes", over the course of the following twenty years the Choctaw were largely forced west of the Mississippi River and into what is now Oklahoma during the period of Indian Removal conducted by the federal government.

The county was named to commemorate Napoleon's victory at the Battle of Marengo over Austrian armies on June 14, 1800.

[1] This name was chosen in honor of the first European settlers, Bonapartists exiled from France after Napoleon's downfall.

[3][4] Other ethnic French who settled here were refugees from the colony of Saint-Domingue, where enslaved Africans and "free people of color" had routed Napoleon's troops and white colonists, and declared independence in 1804.

[1] Situated in Alabama's Black Belt and having a naturally rich soil, the county was developed by planters for numerous cotton plantations, dependent on the forced labor of large gangs of enslaved African Americans.

[5] The fourth-oldest Jewish congregation in Alabama, B'nai Jeshurun, was established in Demopolis in 1858 by immigrants and migrants from other Southern cities.

People left the farms for manufacturing jobs elsewhere, particularly with the wartime buildup of the defense industry on the West Coast.

In addition to seeking jobs, they sought better conditions than the disfranchisement and Jim Crow oppression they faced in Alabama and other states of the South.

Most of the former cotton fields were gradually converted to pastures for cattle and horses, developed into tree plantations for timber and paper production, or transformed into commercial ponds for farming grain-fed catfish.

According to the New York Times, by 2017, the rural Black Belt that stretches across the middle of the state is home to largely poor counties that are predominantly African-American.

[18] Marengo County is home to the Alabama Rural Heritage Center and Chickasaw State Park.