[9]
His father died in the spring of 1791, and he was placed in the care of Robert Morris, an intimate family friend in Philadelphia.[10] He briefly studied medicine at the University of Pennsylvania with Doctor Benjamin Rush and William Shippen Sr.[10] His older brother inherited their father's money, so he lacked the funds for his further medical schooling, which he had also discovered he didn't prefer.[5] He therefore withdrew from medical school, though school archives record him as a "non-graduate alumnus of Penn's medical school class of 1793".[10] With the influence of his father's friend, Governor Henry Lee III, he embarked upon a military career.[11]

Early military career
On August 16, 1791, within 24 hours of meeting Lee, Harrison, age 18, was commissioned as an ensign in the Army and assigned to the First American Regiment.[12] He was initially assigned to Fort Washington, Cincinnati in the Northwest Territory where the army was engaged in the ongoing Northwest Indian War.