Fort Westmoreland was originally a small fort on Spike Island from 1790, and Spike Island Battery. Work on Fort Westmoreland commenced in about 1790 but work was stalled during the Napoleonic Wars with the fort completed in 1802. It was then decided to further expand the fort and new work commences in 1804. This work was completed in 1859 with plans to mount some eighty smooth bore guns in the fort. The Fort has six bastions and ample barrack accommodation. Number 3 Bastion faced the harbour entrance, and was the principal location for the guns.
Fort Westmoreland was upgraded between 1880 and 1881 to mount RML guns. The armament of Fort Westmorland in 1866 was three 12-inch RMLS, two 11-inch RMLs and four 8-inch SB guns.
