At the intersection of Indian trails along Letort Creek, in the eighteenth century the town of Carlisle became the jumping-off point for traders and settlers heading over the Alleghenies on their way west. A brief 1756 encampment at Carlisle preceded the more permanent settlement in May 1757, when Colonel John Stanwix marched upstream with British regulars and provincials during the Seven Years' War (also known as the French and Indian War). After the American Revolutionary War, from 1783–1837, the town of Carlisle was significant as the frontier gateway, as a greatly increased wave of land-hungry migrants moved west.
During the war, numerous substantial brick buildings were erected at Carlisle Barracks for military stores and to accommodate workmen of the revolutionary government's dedicated managing body for the Army, the Ordnance Department. While the facility might have been used to store ammunition and explosives, its lack of access to water transportation made it impractical because of the difficulty of overland travel. The Hessian Powder Magazine, now Hessian Guardhouse Museum, was built in 1777.
In 1794, Carlisle Barracks became the center of intense military activity with the outbreak of the Whiskey Rebellion. President George Washington journeyed to the barracks to review the troops—perhaps as many as 10,000 men. The crisis was posed by farmers in southwestern Pennsylvania, who refused to pay a tax on the commercial whiskey they distilled from their corn crops. They had found corn processed as alcohol more easily transported east over the Alleghenies and more profitable to sell than was corn as grain.
President Washington recommended the barracks as the site for a Federal military academy, but Pennsylvania lost that political battle to the state of New York and its West Point location. The government decided to clear up ownership of the post; in 1801, the government paid $664.20 for the 27 acres (110,000 m²) which it had been renting from William Penn's heirs.
In 1838 the School of Cavalry Practice was established at Carlisle Barracks. It was the army's small but elite mounted force, the forerunner of the Armor School now at Fort Benning, Georgia. Captain E. V. Sumner found most of the barracks buildings in disrepair, the maneuver area less than adequate, and the horses in short supply. Overcoming these problems included drilling his recruits at the double time on foot to simulate the trotting of the missing horses. Another mounted organization, horse-drawn light artillery, also established its school at Carlisle Barracks. In 1839, Captain Samuel Ringgold arrived to begin training recruits and testing equipment for the "flying artillery," as it was sometimes called.