It was one of the larger forts built in a defensive line, 12-20 miles apart, intended to safeguard the more densely-populated communities of the eastern Province of Pennsylvania.

[2]: 70–99 At the beginning of the French and Indian War, Braddock's defeat at the Battle of Monongahela left Pennsylvania without a professional military force.

[5] In late 1755, Colonel John Armstrong wrote to Governor Robert Hunter Morris: "I am of the opinion that no other means of defense than a chain of blockhouses along or near the south side of the Kittatinny Mountains from the Susquehanna to the temporary line, can secure the lives and property of the inhabitants of this country.

The Pennsylvania Provincial Assembly, dominated by Quakers, was reluctant to take military action and refused to pass necessary funding bills to raise troops and construct forts, to the frustration of Governor Robert Morris.

Community leaders demanded protection, petitioning the Assembly to "grant a sufficient Sum of Money to maintain such a Number of regular Troops as may be thought necessary to defend our Frontiers, and build Fortifications in proper Places.

"[6]: 183  On November 26, Governor Morris succeeded in obtaining a grant of sixty thousand pounds from the Assembly, to build a string of defensive forts across central Pennsylvania, and to pay for the training, arming and provision of troops to defend the colony.

"[2] The origin of the name is unclear, but it may refer to Prince William Henry, Duke of Gloucester and Edinburgh, a younger brother of King George III.

[6]: 192 On July 9 1756, Colonel Weiser wrote to Captain Busse ordering the distribution of troops to local farms, to protect men working in the fields at harvest time.

[6]: 322  Because soldiers were frequently detached from the garrison to temporary duty elsewhere, Weiser decided to station a contingent of nine men and a sergeant to remain permanently at Fort Henry.

"[6]: 326–27  When Major Thomas Loyd took command of the eastern line of defense in April 1758, the garrison was reduced to 45 men, and by July to 25.

[15]: 293, 329–30 [6]: 325 Native American war parties continued to attack local farms, killing two or three people at a time and taking children.

[14]: 245  Stone and wood from the fort were removed by farmers to be repurposed, but as late as 1882 remnants of the walls and the cellar of the gunpowder magazine were still visible.