The adventurous French had mapped more territory than their numbers could settle, but their attention soon focused on a section of the valley south of the mouth of the Missouri River.

In the early 18th century, French-speaking immigrants, mostly from Canada, settled villages in the American Bottom such as Kaskaskia, Prairie du Rocher, and Cahokia.

Following the American Revolution and the Treaty of Paris in 1783, the Cahokia region was transferred with the rest of the east bank of the Mississippi from Great Britain to the new United States.

Territorial law books describe the kind of decisions and court cases that were made and heard in this small building.

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.

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.

A visitor center also features exhibits about the area's occupation by the French in the 18th century, as well as the nearby Nicholas Jarrot Mansion.

Due to state budget cuts, the IHPA temporarily closed the Cahokia Courthouse to the public from December 2008 until April 2009.