The Nicholas Jarrot Mansion is a historic house built in the Federal style in 1807-1810. It is located at 124 East First Street in Cahokia, Illinois and is operated as an inactive historic site by the Illinois Historic Preservation Agency (IHPA). It is a State Historic Site, is listed on the National Register of Historic Places, and became a National Historic Landmark in 2001.
As a pro-American merchant with business ties to the new republic, Jarrot was recommended to the westward-bound explorer Meriwether Lewis in 1803. Lewis met Jarrot in December of that year and won the merchant's permission to encamp his men on one of Jarrot's properties, a riverfront tract across from the mouth of the Missouri River. This winter encampment of 1803-1804 became Camp Dubois, the shakedown site of the Lewis and Clark Expedition.
The Jarrot Mansion was built by masons who were not used to working with bricks, and so its windows are slightly askew and the facade of the house is asymmetrical. The house and its facade have an appealing quirkyness, and appear to be more vernacular than the owner may have wished. The house was sturdily built, however, and survived the major earthquakes of 1811-1812 epicentered at New Madrid, Missouri.
The mansion complex includes a spring house built of cut limestone. Spring houses like that of the Jarrot Mansion contained tubs of cool water in which foodstuffs were protected from spoilage for short periods of time.
The Jarrot Mansion is located less than one-half mile from the Cahokia Courthouse State Historic Site, where Jarrot served as judge of St. Clair County.