The One Minute Geographer: The Great Lakes Portage Site Line
The Great Lakes portage line is a bit different from the portage line we looked at along the Fall Line and across the southern US in the previous posts. In the Great Lakes region many settlements developed not only at the farthest point upriver from the Great Lakes that a boat could reach, but also because near that point you could connect to the headwaters of south-flowing rivers. American Indians, and later European trappers, could drag their canoes over the relatively short distance between the headwaters of the rivers that flowed into the Great Lakes to the headwaters of rivers that flowed into the Ohio River system and eventually, the Mississippi River.
Basically this portage line is the divide between the rivers of the Great Lakes basin and the Ohio, Illinois and Mississippi river basins. The red line on the map above shows that divide. When we hear the geographical term “divide” we often think first of the Continental Divide — the summit of the Rockies. That’s true but the term refers primarily to how elevation divides flowing water into different river systems.
So the Continental Divide separates water flowing into the Gulf of Mexico and then the Atlantic from water flowing into the Pacific. You could, in theory, stand on a peak in the rain, facing north, and the water falling on your right foot would flow…