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.
When peace was declared in the War of 1812, the U.S. Army returned to a peacetime establishment at the end of the conflict. That peacetime establishment required a force reduction (a “downsizing” in modern terms) of more than thirty regiments in the infantry alone. The forty-six regiments of infantry were, in 1815, consolidated into eight, mostly by combining the troops from five or more regiments into one unit and renumbering the surviving organizations. The old (pre-1815) 1st Infantry was the oldest unit used to make up the new (post-1815) 3rd Infantry, which created the direct lineage as the Army’s oldest active infantry unit. The commanders of the new units and their numbers were chosen on the basis of seniority. The first commander of the new 3rd Infantry was Colonel John Miller, previously of the 17th Infantry and third in seniority in the Army. The number of the unit became the “3” as a result of Miller’s seniority.