The Cahokia Courthouse was built as a residence around 1740, when present-day Illinois was a colony of France. In 1793 the structure was purchased by the Common Pleas Court of the United States Northwest Territory and subsequently became a center of territorial political and legal activity. The building is historically significant as the oldest courthouse in Illinois and the only one remaining from the state’s territorial period (1787-1818). It is architecturally significant as an example of the French Colonial vertical log poteaux-sur-solle (“post-on-sill”) construction technique.

The Courthouse was moved to St. Louis for the 1904 World’s Fair, and in 1906 to Chicago’s Jackson Park. Each move resulted in losses of original building fabric. Cahokia residents began in the late 1920s to lobby for return of the historic courthouse, leading the state to purchase the building and the land on which it was originally located. The remaining original fabric was returned to Cahokia and incorporated into the building that was constructed on the courthouse foundation. Cahokia Courthouse in 1972 was placed on the National Register of Historic Places.

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.

Cahokia Courthouse hosts special events including an annual Fete du Bon Vieux Temps (“Festival of the Good Old Days”), a colonial Mardi Gras celebration. At the July “Old Time Music Fete,” traditional acoustic musicians perform from the Courthouse porch. Contact the site for details.