Jacques Marquette, a Jesuit missionary, and Louis Jolliet, a skilled cartographer and explorer, set out on an ambitious expedition to explore the Mississippi River. Their journey began in St. Ignace, located in the Michigan Territory, where they assembled a small contingent and canoes to traverse uncharted territories. After navigating through various lakes and rivers, the duo reached the confluence of the Mississippi River, marking a pivotal moment in European exploration of North America. Their expedition commenced in the spring of 1673, demonstrating their desire to find a passage leading to the Pacific and establish vital trade routes.

As they traveled south along the Mississippi, Marquette and Jolliet encountered several Native American tribes, including the Illinois and the Osage. They carefully documented their interactions and collected valuable insights regarding the local geography, natural resources, and indigenous cultures, which would later inform European settlements and bolster trade networks. The explorers noted the river’s width, flow, and the lush, fertile landscapes that lined its banks—details that would prove crucial for future explorers and settlers. Their mapping would eventually aid in the French colonial ambitions in the region as they sought to expand territories and bolster economic interests.

The duo's expedition concluded near the Arkansas River, where they turned back due to concerns about potential conflicts with hostile tribes, securing a wealth of information about the Mississippi’s potential for navigation and resource exploitation. Upon returning, they presented their findings to French authorities, emphasizing the strategic importance of the river as a trade route and a key asset for territorial expansion. Their detailed maps and reports established a foundational understanding of the river, setting the stage for future exploration and colonization in the wider Mississippi Valley.