Chicago Portage

The Chicago Portage was an ancient portage that connected the Great Lakes waterway system with the Mississippi River system. Connecting these two great water trails meant 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.

In the summer of 1673 members of the Kaskaskia, a tribe of the Illinois Confederation, led French explorers Louis Jolliet and Father Jacques Marquette, the first known Europeans to explore this part of North America, to the portage.  A strategic location, it became a key to European activity in the Midwest, ultimately leading to the foundation of Chicago.

In 1848, the water divide was breached by the Illinois and Michigan (I&M) Canal cutting through the portage.

Created by a glacier

The history of the Chicago Portage begins at the end of the last Ice Age. It was formed as the Wisconsin glaciation retreated northward about 10,000 years ago, leaving behind Lake Chicago (now called Lake Michigan), which was created from the glacier's meltwater.

As the glacier melted and retreated, the water in Lake Chicago rose until it overflowed the southwestern edge of the Valparaiso Moraine, which encircles the lake's southern half, creating the Chicago Outlet River. This was a substantial river, comparable to today's Niagara River, and over time it carved the channel later used by the main and south branch of the Chicago River, the Des Plaines River, and the terrain that became the Chicago Portage.

As the glacier continued to retreat, it opened another outlet far to the East that became the St Lawrence River.  This allowed the emerging lakes to drain even faster, and the Chicago Outlet River dried up leaving the gap in the moraine that created the Chicago Portage.

This process created the Chicago Portage, a link between what became known as the Chicago River and what became known as the Des Plaines River. The point at which the portage crossed the low continental divide that separated waters flowing east toward Lake Michigan from waters flowing west toward the Mississippi River was a wetland that occupied the ancient stream bed of the Chicago Outlet River.  Early settlers called this marshy area “Mud Lake”.  The total length of the portage was about six miles.

Mud Lake could be wet, dry, marshy, or frozen, depending on the season and the weather, making it a difficult, albeit very valuable, transportation route. In very wet weather the water level in both the Des Plaines River and the Chicago River would rise to the point that Mud Lake was flooded, and travelers could traverse the entire six miles by canoe.  Usually, however, particularly in late Summer, it was necessary to pull out canoes at some point and carry them and all supplies around Mud Lake.

A key to travel and trade in North America

The Chicago Portage allowed easy access, by boat, to almost all of North America, from the mouth of the St Lawrence River to the Rocky Mountains and the Gulf of Mexico.

The St Lawrence River divide

Until the second half of the nineteenth century water transportation was virtually the only way to move trade goods and people around North America.  Therefore, connections between strategic waterways, usually involving portages, held special importance.

The importance of the Chicago Portage lies in the fact that the channel cut by the Chicago Outlet River created an easy passage over the Saint Lawrence River Divide, the continental divide that separated what had become the Great Lakes waterway system from the Mississippi River waterway system and, as the illustration shows, opened up almost all of what was to become the United States from the Allegheny Mountains to the Rocky Mountains as far south as the Gulf of Mexico.

Early peoples

Native Americans had used the portage for thousands of years before the arrival of Europeans. They found the Chicago Portage to be a convenient transportation route between the shores of Lake Michigan and the Mississippi River in the interior. The map shows that the most important trails in the region led to the portage and the several fords near it.

The map also shows the Old Portage Long trail that was used when there was insufficient water in Mud Lake to allow traverse by canoe.  This trail extended to the southwest to the early settlement of Ottawa on the Illinois River.  Since there was usually sufficient water in the larger Illinois River for canoeing, this “Ottawa Trail” was used in very dry conditions when there was insufficient water in the Des Plaines River.

The first Europeans

By 1673 the French had established a trading post at present day Mackinac Island at the top of Lake Michigan. In that year, the first Intendant (administrator) of New France, having heard of reports of a great river to the West and hoping it would be the long-sought "Northwest Passage" to the Pacific Ocean, ordered a reconnaissance mission to find and explore this river. In May of that year the group, consisting of Louis Jolliet, Father Jacques Marquette, and five voyageurs set out on their voyage of discovery.

The explorers found the Mississippi River, explored it, and then returned to Michilimakinac by a different route on the advice of Native Americans they had encountered along the way, who told them that there was a better way to return to Lake Michigan. Travelling by stages up the Illinois River to the Des Plaines River, in September 1673 members of the Caskaskia, a tribe of the Illinois Confederation, led Jolliet and Marquette to the western end of what became known as the Chicago Portage.

During the 18th century, the Chicago Portage was one of the most strategic locations in the interior of the North American continent for the French. Particularly it provided an easy connection between the French cities of Montreal and New Orleans