John Graves Simcoe, the first Governor of Upper Canada, planned for defences for the mouth of Toronto Harbour, at Fort York, and with a Gibraltar Point Blockhouse, on the south bank of the entrance.
In 1800 a storehouse and guardhouse were added, but the battery was destroyed in 1813 and rebuilt as a blockhouse in 1814. The blockhouse was two storeys tall, with the upper platform having no roof and with its floor consumed with a traversing carriage for a single cannon. An oven permitted supplying the cannon with "hot shot"—cannonballs heated so they could start fires on the highly inflammable ships of the era. The lower floor could barrack thirty staff. The blockhouses walls were formed from two parallel wooden walls, with the gap in between was filled with tightly packed earth.
The blockhouse played no active part in the defence of York, when it was captured during the War of 1812.
During peacetime the barracks at the Gibraltar Point Blockhouse were used to quarantine seriously ill individuals.
The blockhouse was in ruins by 1823 and removed by 1833.