| St. Clair | Cahokia Mounds (missing) | 01/01/1934 |
| St. Clair | Cahokia, Illinois | 01/01/1978 |
| St. Clair | Deneen Family, The | 12/05/1966 |
| St. Clair | East St. Louis Race Massacre, July 1917 | 06/24/2023 |
| St. Clair | French-Colonial Home Site of Jean Baptiste Hamelin | 07/04/2013 |
| St. Clair | Friedrich Franz Karl Hecker (1811-1881) | 03/25/2023 |
| St. Clair | Gustavus Koerner | 01/01/1976 |
| St. Clair | Illinois in the American Revolution | 07/03/1976 |
| St. Clair | John Jacob Hays (1770-1836) | 05/17/2019 |
| St. Clair | John Messinger, 1771-1846 | 07/12/1981 |
| St. Clair | McKendree College | 01/01/1978 |
| St. Clair | Mississippi Bubble, The | 07/05/1967 |
| St. Clair | Pensoneau-Caillot Pioneer House | 01/01/1965 |
