Frontier forts helped open the vast territory west of the Allegheny Mountains to settlement, especially during the 40 years between 1754, when Capt. William Trent first attempted to fortify the Forks of the Ohio River, now Pittsburgh, and 1794, when the Indians were defeated by Major-General Anthony Wayne at Fallen Timbers. Scattered across the frontier, these forts served as havens of refuge for early settlers subject to periodic Indian attacks. They fell into two main types: larger forts built to house military units and supplies, such as Fort Pitt and Fort Ligonier, and smaller blockhouses with a few portholes, built by one family but also used by neighboring families when under attack. In a May 4, 1774, letter to George Washington, his grist mill partner Gilbert Simpson wrote that the country was in great confusion because the Indians had declared war, that at least 500 families had left within the past week, that there had been several skirmishes between white people and Indians, and that he believed it had been the white peoples fault altogether. Simpson said he intended, with the help of neighbors, to build a fort where he lived while continuing work on Washington's mill. Fort Trial is a replica of the blockhouse type most likely built there by Simpson on Washington's Bottom, and its name comes from letters in which Simpson lamented that life on the frontier was a great trial. By September 24, 1774, Simpson reported that his son had returned safely with the money to continue building the mill and asked Washington how he would have the mill let when it was ready.