Based on North American Forts; original sources needed.
With additional information from Wikipedia:Brownsville, Pennsylvania
Fort Redstone, also known as Redstone Fort, was located at the end of a natural path down the heavily forested western slopes of the Western Allegheny ridgeline and its western foothills.
Where that path crosses the Monogahelia, the river has undercut the surrounding sandstone cliffs creating a broad shelf adjacent to the river edge, reduced the depth of the river itself, and slowed its speed. This gave travellers both easy access to the river, and made it fordable using using poleboats or scratch-built timber rafts. As a result this was a natural site to establish a fort during the French and Indian War, when the English and French were contesting ownership of the area.
The Virginia militia constructed a wooden stockaded fort at this location in in 1754. It was probably built on the site of an earlier Amerindian construction of the "Old Forts" type <re name="OldFort">Old Forts is a generic term used by the colonists to describe Amerindian mounts and earthworks. Such construction may have had military uses for the Indians, but most were cultural features. The Amerindians probably established a site here largely for the same reason the settlers did: easy access, and fordability of the river.</ref> Known as Fort Redstone it was used as a supply base for Fort Prince George. It was not in service long, as the French destroyed it in June 1754, soon after construction. The PA mlitia rebuilt it as in 1759 as "Fort Burd", named for its commanding officer. This version of the fort included a moated stockade with bastions, and log barracks. It served its purposes until the end of the French and Indian War, and was abandoned in1763. The Virginia state militia probably made use of the site during Dunmores War in 1774. During the Revolution (1778) it was used as a militia supply depot. After the Revolution it was turned to civilian uses, first as a trading post in 1786, and later rebuilt as a home, the Nemacolin Castle, a large stone mansion with an octagonal tower with battlements. Today it is operated by the Brownsville Historical Society, as an historic site.