Harsen migrated from Albany, New York in about 1779, during the American Revolutionary War, with his daughter and son-in-law Isaac Gerrit Graveraet (or Graveret)[6][7].

The 1783 Treaty of Paris, which ended the American Revolutionary War, described the international boundary line with imprecise terms in several places, including the mouth of the St. Clair River.

In the most commonly known map of the area from that period, made by John Mitchell in 1755 and which was used in negotiating the treaty, the delta and all the islands at the mouth of the St. Clair River are absent.

Some persons located in the new United States who did not want to renounce their status as British subjects following the war moved to make their residences there.

In 1870 a case arose involving Hiram Little of Wallaceburg, Ontario, a captain who was given a contract to provide cord wood and supplies to a work crew.

After searching of documents, including contact with the Crown in England who supplied early charts of the area, Capt.

To avoid further embarrassment, the U.S. officials moved the international boundary east, further infringing on Canadian (and First Nations) land.

Some observers still disagree as to which nation should legally "own" Harsen's Island and the St. Clair delta area.

[2] The St. Clair Flats supports a range of wildlife, such as the great blue heron, snapping turtles, watersnakes, muskrats, mink, whitetail deer, pintail, canvasback and mallard ducks, Canada geese and red-winged blackbirds.