The original military fort was built, as the headquarters of the British garrison, between 1775-1779, to secure St John's from attacks, from the French, as well as from American privateers, and it was abandoned in 1871.
The vulnerability of Fort William had been revealed when the French captured it in 1762, The American Revolution had increased the need to improve St. John's defences.
By 1779 Colonel Robert Pringle of the Royal Engineers, and Commandant of the garrison, had completed the construction of Fort Townshend, which Governor Lord Shuldham had begun in 1773.
Fort Townshend was enlarged and strengthened in 1796, because of a war with France, "as part of changes made to the entire defense system".
[1] After garrison was withdrawn 1871 the fort had been allowed to decay,[2] and the site became the home of the Royal Newfoundland Constabulary and, later, the St. John's Fire Department.