Before the canals were built, what problems were present at the portage site?

In 1673, a French missionary and a French-Canadian explorer — Father Jacques Marquette and Louis Jolliet — were returning to Canada after a mapping expedition that had brought them along the Mississippi River into present-day Arkansas and Mississippi. They paddled upstream in their birchbark canoes, headed for the Fox River and Green Bay, until some local Miami people tipped them off to a valuable shortcut. If they headed instead for the Illinois and Des Plaines Rivers, they would come to a portage where they could carry their canoes across a few miles of swampy marshland and arrive at the Great Lakes in a fraction of the time.

Marquette and Jolliet paddled to what is now the suburban town of Lyons, slogged across the muddy portage to the Chicago River, put their boats back in the water, and continued on to Green Bay.

Jolliet immediately recognized the significance of the portage. The shortcut could accelerate travel and trade between the Great Lakes and the Mississippi River, the two major transportation networks of the North American continent.

A city built at the mouth of that canal would be poised for greatness.

“We could easily sail a ship to Florida,” he wrote in his journal. “All that needs to be done is to dig a canal through but half a league of prairie from the lower end of Lake Michigan to the River of St. Louis [today’s Illinois River].”  

Word of the “Chicago Portage” spread quickly, and it soon became a popular route for French and British fur traders and missionaries.