I have property on the edge of this former wetland. It's a large sand dune, as are most of any hills in this area. It's a really unique area. We have a river in town that comes south out of Michigan, then turns north again and runs to Lake Michigan, about 30 miles away. On the north and east sides of town, all drainage goes into that river, and eventually goes over Niagara Falls, and out into the North Atlantic. On the west and south of town, all drainage goes towards the Kankakee river, which drains into Illinois, where it joins the Des Plaines River to form the Illinois River. That empties into the Mississippi, which drains into the Gulf of Mexico. Southeast of town, around the OP's area, things drain into the Yellow River, which drains into the Kankakee River about 50 miles southwest of here.
So, most people don't know it, but there's a continental divide running through South Bend, Indiana.