The village and county are named after statesman Lewis Cass, a New Hampshire native and a prominent U.S. senator from Michigan prior to the American Civil War.

Cassopolis is part of the South Bend–Mishawaka, IN-MI, Metropolitan Statistical Area sometimes referred to as Michiana.

Cassopolis was a transit point on the Underground Railroad, by which sympathizers aided refugee slaves from the South to gain freedom in the North and in Canada.

Some refugees continued through Michigan to settle in Canada in order to avoid risk under the 1850 Fugitive Slave Law, which increased incentives for capture.

In the 1960s, a group of African Americans connected to the Nation of Islam acquired some 1,000 acres of farmland in the area.

Work on this acquisition was overseen by a man who had graduated from Cassopolis High.

As of the census[11] of 2010, there were 1,774 people, 709 households, and 384 families residing in the village.

40.8% of all households were made up of individuals, and 17.7% had someone living alone who was 65 years of age or older.

As of the census[2] of 2000, there were 1,740 people, 703 households, and 437 families residing in the village.

33.9% of all households were made up of individuals, and 11.8% had someone living alone who was 65 years of age or older.