Following the explorations of Marquette, Jolliet and La Salle in the 1670s, the Mississippi Valley became part of
New France. 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 this region, which would later be known as the
American Bottom, the
alluvial soil was exceptionally fertile, and the local Native Americans, members of the
Illiniwek nation or Illinois Confederacy, were friendly to the newcomers. 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. They lived in harmony with the Indians and named several of their villages, such as Cahokia, after constituent tribes of the Illiniwek who lived nearby. The building now known as the Cahokia Courthouse traces its ancestry back to a French-Canadian
log cabin built by one of these settlers about 1740. In line with his group's customary architecture, the unknown builder built the cabin with logs raised vertically. This was different from having the logs placed horizontally, as had become the custom among English-speaking frontiersmen farther east. The French colonial building style is called
poteaux-sur-sol (French:post on sill) construction, with the building's posts grounded in a foundation
sill to retard wood rot. ==American Bottom==