Old Cahokia Courthouse: Illinois's Oldest Building

The building at the edge of Cahokia was assembled around seventeen thirty-seven to seventeen forty when this land was a colony of France. Jean le Poincet built it as a private home using the poteaux-sur-solle technique, vertical logs set on a wooden sill rather than driven into the ground, a French colonial construction method of which only thirty examples survive in the United States. In seventeen ninety-three the Common Pleas Court of the Northwest Territory purchased it and turned it into the region's first courthouse.

It is the oldest building in Illinois and the only courthouse surviving from the state's entire territorial period, from seventeen eighty-seven to eighteen eighteen. In nineteen oh four the structure was moved to Saint Louis for the World's Fair. It later traveled to Chicago's Jackson Park before returning to Cahokia, where it now stands as a state historic site.