How Michigan Ended Up With Isle Royale

Look at a map of the Great Lakes and Isle Royale seems to be in the wrong state, or even the wrong country.

The island sits in the northwestern corner of Lake Superior, about 15 miles from Minnesota and roughly the same distance from Ontario. Michigan’s Upper Peninsula is over 50 miles away.

So how did this remote island become part of Michigan?

The story begins with three Founding Fathers negotiating the end of the American Revolution.

In 1783, Benjamin Franklin, John Adams, and John Jay were in Paris negotiating peace with Great Britain. Among their tasks was determining where the new United States would end and British territory would begin.

The boundary they negotiated crossed the Great Lakes. When it reached Lake Superior, the Treaty of Paris became surprisingly specific. The line was to continue through the lake “northward of the Isles Royal & Phelipeaux.”

“Isles Royal” was Isle Royale.

The treaty explicitly placed the international boundary north of the island, putting Isle Royale on the American side.

But there was a problem with the other island named in the treaty.

Phelipeaux did not exist.

Franklin, Adams, and Jay were working with the best geographic information available to them, including the influential Mitchell Map published in 1755 used during the peace negotiations.

Lake Superior was still imperfectly mapped. Isle Royale appeared out of position, and nearby was another substantial island labeled Phelipeaux.

It was a phantom island, copied from earlier maps despite never having existed. Yet it was convincing enough to become part of the language defining the boundary of the U.S.

There is also a long-running story that Franklin deliberately pushed the boundary north of Isle Royale because he knew the island contained valuable copper. Isle Royale certainly has native copper, and knowledge of copper deposits around Lake Superior long predates the U.S.

Whether Franklin’s knowledge of that copper influenced the boundary may simply be lost to history. The treaty itself is clear: Franklin, Adams, and Jay negotiated and signed an agreement that specifically directed the international boundary north of Isle Royale.

That answers why Isle Royale is in the U.S. It doesn’t explain why it is in Michigan.

Michigan Territory was created in 1805, and its boundaries changed repeatedly as the country organized new territories and states around the Great Lakes.

By the 1830s, Michigan was seeking statehood while fighting Ohio over the Toledo Strip. Congress ultimately awarded Toledo to Ohio and added the western portion of the Upper Peninsula to Michigan as part of the settlement clearing the way for statehood.

That produced the familiar story that Michigan traded Toledo for the Upper Peninsula.

But Isle Royale’s place in Michigan came down to the actual boundary Congress drew.

In 1836, Congress defined Michigan’s western boundary across Lake Superior, running from the international boundary toward the mouth of the Montreal River on what is now the Wisconsin border.

Isle Royale was east of that line.

When Michigan became the 26th state on January 26, 1837, Isle Royale was inside its boundaries.

Minnesota Territory wouldn’t be created for another 12 years. Minnesota itself wouldn’t become a state until 1858.

There is one more distinction worth making. The 1783 Treaty of Paris established the international boundary, but it did not settle Indigenous title to Isle Royale. That was addressed through two later agreements with the Ojibwe: the 1842 Treaty of La Pointe and the 1844 Isle Royale Compact.

Today, the entire island is part of Isle Royale National Park, along with hundreds of smaller surrounding islands. But the reason this remote island so close to Minnesota and Ontario appears on a map of Michigan reaches all the way back to the American founding.

And tucked into the treaty that first put it on the American side is one of the stranger details of the story: Franklin, Adams, and Jay drew the new nation’s boundary north of two named Lake Superior islands.

One was Isle Royale.

The other existed only on their maps.