The Strange, True Story of How Michigan Accidentally Gave Wisconsin a Chunk of the U.P.

The story of how Michigan got the Upper Peninsula has a stranger footnote that even most Michiganders don’t know: after all that, Michigan accidentally handed a piece of the U.P. back to Wisconsin — and the U.S. Supreme Court had to clean it up.

Here’s what happened. After the Toledo War settlement gave Michigan the Upper Peninsula, somebody had to actually go survey the border between the U.P. and the new Wisconsin Territory. The agreed-upon boundary was supposed to follow a specific river — the Montreal River — up toward Lake Superior. But the Montreal River splits into two branches, and the surveyors, out in genuine wilderness with primitive tools, followed the wrong branch. The mistaken line handed a sizable wedge of land to Wisconsin that, by the original agreement, arguably should have been Michigan’s.

For decades, nobody much cared — it was remote, forested country. But then prospectors realized that same region was loaded with valuable iron ore. Suddenly Michigan very much wanted it back. The dispute simmered until the U.S. Supreme Court finally settled it in 1926, ruling that Wisconsin could keep the land. The Court’s reasoning was partly practical: the people living there had been Wisconsinites for generations, building their lives under Wisconsin’s government, and uprooting all of that over a 90-year-old surveying mistake would cause more harm than good.

So the next time someone tells you the U.P. border is a clean, logical line, you can tell them the truth: part of it is where it is because somebody, long ago, took a wrong turn at a fork in a river — and the highest court in the land decided to just let the mistake stand.