Potawatomi Indians originally inhabited what is today Countryside. Comprised of fertile farmland, the area remained largely unsettled until the first residential subdivision was built in the late 1940s. The City was not officially incorporated until 1960.

The famous Marx Brothers have ties to Countryside, having owned a chicken farm in the area near Joliet Road (Route 66) and Lagrange Road. The farm was never an economic success. Groucho Marx claimed it was because the brothers spent too much time watching the Chicago Cubs at Wrigley Field.