Caseyville is a village in St. Clair County, Illinois, United States.

There were deposits of coal in the area, and Harbour was one of several members of the Illinois Coal Company, along with Zadok Casey, Walter Seates, Malcomb Robinson, Charles Barrett and John Roy.

Casey had held several offices including United States Representative and Lieutenant Governor of Illinois.

In 1849, the Illinois Coal Company founded the town and named it for Casey.

25.8% of all households were made up of individuals, and 12.6% had someone living alone who was 65 years of age or older.