Chicago Portage

The Chicago Portage was an ancient portage that connected the Great Lakes waterway system with the Mississippi River system. This connection provided comparatively easy access from the mouth of the St. Lawrence River on the Atlantic Ocean to the Rocky Mountains and the Gulf of Mexico. The approximately six-mile link had been used by Native Americans for thousands of years during the Pre-Columbian era for travel and trade.

During the summer of 1673 members of the Kaskaskia, a tribe of the Illinois Confederation, guided French explorers Louis Jolliet and Jacques Marquette—the first known Europeans to explore this part of North America—to the portage. A strategic location, it became important to European exploration in central North America, resulting ultimately in the founding of Chicago.

The portage crossed waterways and wetlands between the Chicago River and the Des Plaines River, through a gap in the Valparaiso Moraine. In 1848, the water divide was breached by the construction of the Illinois and Michigan (I&M) Canal through the portage; this was deepened and widened in 1900 by the Chicago Sanitary and Ship Canal which was also used to reverse the water's directional flow.