In the spring of 1673, French explorers Louis Jolliet and Jacques Marquette set out from the mission settlement of St. Ignace, in present-day Michigan, to explore the Mississippi River. Marquette, a Jesuit missionary, was eager to spread Christianity among Indigenous groups, while Jolliet was a seasoned cartographer and fur trader. Their journey was motivated by a desire to map the Mississippi River, understand its geography, establish trade routes, and seek opportunities for converting Indigenous peoples to Christianity.

The expedition began in mid-May 1673 with a small party of five men and two canoes. They navigated the waters of the Great Lakes before entering the Wisconsin River, which would serve as their primary waterway leading them southward into the Mississippi. Along the way, Jolliet and Marquette documented their interactions and observations of the various tribes they encountered, including the Illinois and the Osage. They aimed to gather information about the river's course and the potential for trade with the French in Canada.

Their explorations were significant not only for cartographic records but also for laying groundwork for future French claims in the region. The duo’s understanding of the river's vast network allowed for future expeditions and eventually contributed to France's imperial ambitions in North America. They traveled over 2,500 miles of the river system, marking a considerable advancement in the knowledge of North American geography and Indigenous cultures. Jolliet’s maps and accounts served as critical resources for later explorers and settlers in the continent.