This History of the 1st American Regiment is from the U.S. Army website: www.army.mil
The US Army's oldest infantry regiment, The Old Guard, was created on June 3, 1784 as a result of the 1783 Peace of Paris. The provisions of the treaty ending the war between Great Britain, France, and the colonies of British America (Americans know the war as the American Revolution) was the requirement that the newly independent colonies take military control and civil responsibility for the land west of the Appalachians. This area is now occupied by the states of Ohio, Iowa, Indiana, Wisconsin, and Michigan, and the border along the Great Lakes with British controlled Canada. At the time, Native Americans and their British allies inhabited this region.
The American army that had won the Revolution (with the help of a French army and French fleet) had been largely disbanded and the troops returned to their respective states in the spring of 1784. The Commander-in-Chief bid good-bye to his officers, and returned to his Virginia farm on the Potomac River. A single, small artillery detachment, posted to West Point, was retained from the Continental Army. For practical purposes, there was no force left to defend the United States. Congress was forced, because of the provisions of the Treaty of Paris, to create an army. The single unit created became The Old Guard.
The troops of the new unit, probably not more than 450 men, and the officers, never more than a few dozen in the first years, were the last of the troops from Connecticut, New Jersey and Pennsylvania who were induced to enlist (having first been mustered out of the old Army.) The officers held their commissions from the states from which they came, since there was no legislation authorizing the Confederation of States to issue commissions. These were the beginnings of the national defense and the United States Army.
The Treaty of Paris required that the United States accomplish three missions. First, to receive the garrisons west of the Ohio River held by the British Army, and to garrison some of those forts. Second, to control the flow of settlers (and “squatters”) from the east, a large number of who were claiming lands offered to them in lieu of Continental Army pay long in arrears. And lastly, to attempt to control the inevitable clashes between the Indians and the settlers and land speculators. The force that was created in 1784 to accomplish these missions was called the First American Regiment.
The First American Regiment began to train at a series of forts along the Pennsylvania frontier in the fall of 1784. The first commanding officer, Lieutenant Colonel Josiah Harmar, began to plan a campaign to subdue the Indians and then force the departure of the British garrisons. His efforts in the next years--and those of other commanders in later years--met with only limited success and two catastrophic defeats--Harmar’s defeat in October 1790 with the First American Regiment and St. Clair’s defeat in November 1791 with the new 2nd Infantry--largely because of tactical mistakes and a weak national government that could not adequately support sustained military operations on the frontiers.
For the first twelve years of the existence of the Regiment, it fought under several names. Created as the First American Regiment in 1784, it was also known as the Regiment of Infantry in 1789, the 1st Infantry after the raising of the 2nd Infantry in 1791, the Infantry of the 1st Sub-Legion of the Legion of the United States in 1792, and again as the 1st Infantry in 1796.
The Legion of the United States was a combined arms organization consisting of highly trained and specialized Infantry, Artillery, and Cavalry. Under the command of Pennsylvanian (and stern disciplinarian) Major General Anthony Wayne, the Legion finally broke the back of Indian resistance to settlement in the Old Northwest at the Battle of Fallen Timbers in August 1794. One eventual outcome of the Battle of Fallen Timbers was that the British were finally forced to surrender Detroit, their last garrison in the United States, in 1796. The mission accomplished, the Legion was broken up and the Regiment again became the 1st Infantry.