The Diocese of Belleville includes churches in Alexander, Clay, Clinton, Edward, Franklin, Gallatin, Hamilton, Hardin, Jackson, Jefferson, Johnson, Lawrence, Marion, Massac, Monroe, Perry, Pope, Pulaski, Randolph, Richland, Saline, St. Clair, Union, Wabash, Washington, Wayne, White, and Williamson Counties.
An online finding aid to the microfilm is available through the St. Clair County (Illinois) Genealogical Society. The collection is now available through FamilySearch: Illinois, Diocese of Belleville, Catholic Parish Records, 1729-1956