After Braddock's crushing defeat, Washington led the survivors back to Virginia. Virginia's House of Burgesses on August 6th authorized the formation of Ranger Companies to help defend the frontier, which was now under fierce attacks from Indians. Captain William Cocke and Captain John Ashby were given command of the 1st and 2nd Company Rangers respectively, and they set out to recruit men for their Companies. By mid-October, Ashby had 33 Rangers under his command. After receiving orders to build his Fort, Ashby and his men quickly completed construction by the beginning of December, knowing that winter was fast approaching and desiring protection from the Indians.
Captain Ashby's Rangers had three primary responsibilities. The first was to protect any settlers in the immediate area along Patterson Creek, about five miles southwest of where it flowed into the North Branch of the Potomac. According to Washington's letters, most of the Patterson Creek residents had either fled or had been killed by the time Ashby's Fort was built. The second responsibility was to escort supply wagons and couriers along the road between Fort Cocke, 12 miles upstream on Patterson Creek, and Fort Cumberland, about the same distance north along Wills Creek, which is present-day Cumberland, Maryland. Washington also ordered Ashby to send out patrols in search of enemy French or Indians. The Rangers continued these duties until their enlistments were over in September 1756.
Washington tried unsuccessfully to retain the Rangers, asking them to join the Virginia Regiment, but they all left when their enlistments were up. Ashby's Fort was manned after this by soldiers from the Virginia Regiment until April 16th, 1757, when Governor Dinwiddie repositioned the men along Patterson Creek to Forts along the South Branch of the Potomac in the Trough. The Fort was never occupied again. In 1758, England sent General John Forbes to do what Braddock failed to do - take Fort Duquesne. Forbes found success on November 25th, 1758 when he found that the French had abandoned and burned Fort Duquesne in advance of Forbes' superior numbers. When the Indians saw the French retreat, they perceived this as a major weakness, and attacks on British Colonials were dramatically reduced, eliminating the need to continue manning the Forts. While the war would not officially end until 1763, large-scale fighting ended five years earlier.
One of Ashby's original Rangers was Daniel Morgan, who went on to become a brilliant General in the Revolutionary War, and later a Congressman from Virginia. In 1794, Morgan was promoted to Major General and was selected to lead troops to put down the Whiskey Rebellion in western Pennsylvania. Morgan camped with his troops at the site of Fort Ashby on the way.
The site is now overseen by the Friends of Ashby's Fort, a 501(c)3 non-profit organization. A museum is located in a 1780s log building which was probably a barracks for one of the two later Forts built in the same location as Ashby's Fort.