The Cahokia Courthouse State Historic Site is a reconstructed French-Canadian structure built about 1740 at what is now 107 Elm Street, Cahokia, Illinois. At various times, it has served as a house and as a courthouse. It is currently interpreted to resemble its appearance about 1800 as a frontier courthouse of the Northwest Territory. The courthouse was listed on the National Register of Historic Places on November 9, 1972.

In 1904, promoters for the St. Louis World’s Fair discovered the old Cahokia courthouse, which by this time had become one of the oldest surviving buildings in Illinois. They bought it, dismantled it, and carried the surviving posts and other wooden pieces across the river to St. Louis for rebuilding as a fair attraction.

The courthouse appears to have survived this experience and to have excited interest from Illinoisans. At the end of the fair, the cabin was again dismantled, this time for a 1906 rebuilding in Jackson Park in Chicago.

Cahokia residents resented the fact that their oldest building had been moved to the opposite end of the state, and successfully lobbied in the 1920s for the old log cabin to be purchased and reconstructed a third time on its original site.