This courthouse is an authentic remnant of the French settlement of Illinois and an excellent example of their "post-on-sill" foundation style of construction. Originally constructed as a dwelling in 1737.

The building, listed on the National Register of Historic Places, now known as the Cahokia Courthouse traces its ancestry back to a French-Canadian log cabin built by one of these settlers. In line with his group's ethnic custom, the unknown builder built the cabin with logs raised vertically, rather than horizontally as had already become the custom among English-speakeing frontiersmen farther east. This building style is called poteaux-sur-solle construction, with the building's posts grounded in a foundation sill to retard wood rot.

The vertical-log Courthouse has a double-pitch roof of cedar shingles and galleries on all four sides. Inside are three exhibit rooms and another furnished to represent the courtroom in the 1790s. Exhibits in the Courthouse depict issues that came before the court around 1800 and a history of the structure as it was moved in the early twentieth century to St. Louis and Chicago before its eventual return to Cahokia. Interior features include two massive limestone fireplaces, shuttered casement windows, and French-style doors.

The Courthouse staff and volunteers provide guided tours, or guests may experience the site at their leisure. Exhibits in the Courthouse depict issues that came before the court around 1800 and a history of the structure as it was moved in the early twentieth century to St. Louis and Chicago before its eventual return to Cahokia. The Courthouse is not fully disabled accessible. The visitor center houses exhibits depicting the Jarrot Mansion, currently undergoing restoration, and placing area historic sites within the context of the eighteenth-century French occupation.