Does Illinois share a border with Michigan (AKA who owns the Great Lakes)?

1st Question: What are the borders of the Great Lakes states?
2nd Question: Why were the borders drawn up like that?
3rd Question: Who owns the Great Lakes?

Most of us learned memorized the location of all fifty US states some time in grade school. Some of us were even able to recognize or draw the shape of the all the US states. But something odd happens to the shape of states around the Great Lake. I'll use Illinois and Indiana as an example.

Now 5 states were formed from the old Northwest Territory, a region north of the Ohio River and east of the Mississippi: Ohio, Michigan, Wisconsin, Illinois, and Indiana. (Parts of it did become Minnesota.) The guidelines for how the states should be created from the NW Territory is contained in the Northwest Ordinance of 1787. One part of this ordinance states the region could be divided into northern and southern states by a boundary

"which lies north of an east and west line drawn through the southerly bend or extreme of Lake Michigan"


If those words were followed precisely, then the states of Illinois and Indiana would look like the graphic on the right. Chicago would have ended up in Wisconsin and the shapes of those 2 states would obviously be different.

So how did these states end up with different borders? There are well known stories about how the northern borders got extended further north than the southerly end of Lake Michigan.

Indiana supposedly wanted more usable lakeshore. Using the original guidelines, they would not have any access to Lake Michigan. So the state extended the border 10 miles north when its boundaries are described in its state constitution. Congress followed suit on June 23, 1836 when they agreed to this 10 mile northerly deviation. But what about Illinois?

The change in the Illinois northerly boundary is attributed to Nathaniel Pope, the states first (territorial) delegate to the US Congress. While Congress was debating the Act to admit Illinois as a state into the Union, Pope suggested that the northern boundary be moved from the southernly end of Lake Michigan to a parallel at 42 degree 30 minutes.

Various reasons were given to move the boundary. Politicians then were already concerned of a potential rift in the Union between Northern and Southern states. Pope may have argued that isolating Illinois from Lake Michigan would force the state to use the Mississippi and Ohio Rivers for commerce which would make it dependent on Southern States. By having access to Lake Michigan, it could form relationships with other northerly states such as New York or Pennsylvania. The Annals of Congress (April 4, 1818) describe Pope arguing that giving Illinois access to Lake Michigan would connect it to northern states and "would afford additional security to the perpetuity of the Union". He also argued that the new northern border would include Fort Dearborn (being rebuilt) at the Chicago River in the newly created state and increase the interest of creating a canal between Lake Michigan and the Mississippi River next to Chicago. Congress agreed to the changed boundary.

So who owns the Great Lakes? Well, regional maps rarely show the boundaries of the states as they extend into the Great Lakes such as the northern boundaries of Illinois and Indiana which actually extend into Lake Michigan. These added area of Lake Michigan can be included in the representations of the states to better understand how the Great Lake states related to each other.

So the shapes of the Great Lake states go from this:

to this:

But I doubt anyone will learn them this way. Most lakes that cross a state boundary are not big enough to cause a significant change in the boundary of states (exception being Lake Tahoe). The Great Lakes are the exception. States extend into them. So if you're drawing the state of Illinois, don't forget the piece the sticks out north and east of Chicago. Besides Ohio, Indiana and Wisconsin, Illinois also borders Michigan. It just happens in the middle of Lake Michigan.