Sources vary as to McArthur's exact birthdate. It has been given as January 14, 1772, or June 14, 1772. He was born to Scottish immigrants in
Dutchess County in the
Province of New York, McArthur grew up in western
Pennsylvania and later moved to
Kentucky, where he was employed as an Indian ranger. McArthur and his friend
Alexander McGuffey volunteered in 1790 at Fort Pitt for expeditions against Native Americans during the
Northwest Indian War, serving as a scout under Generals
Josiah Harmar and
Anthony Wayne. McArthur obtained a position with
Nathaniel Massie in 1793, and worked with Massie on a surveying expedition in the Northwest Territory. In 1796, he worked with Massie to lay out the new town of
Chillicothe, Ohio, The British paroled him and McArthur returned to Ohio. He was appointed a
brigadier general in the
U.S. Army. Shortly thereafter he was placed in charge of the
Army of the Northwest following Harrison's resignation. McArthur did not face much action after that, but he was engaged in negotiating treaties with the Indians. In 1817, he was one of two commissioners (along with
Lewis Cass) who negotiated the
Treaty of Fort Meigs, which was signed September 29 of that year with several
Native American tribes. ==End of War of 1812==