The Stone Fort, as it is known, was built during the 1830s by the Hudson's Bay Company. They had already built a fort at the forks of the Red and Assiniboine Rivers in 1822, but spring flooding was such a problem that the company looked for a better location down river. It turned out to be a mistake, because the other site was much better, so in 1836 the HBC went back to the forks and did most of their business out of Upper Fort Garry. The upper fort was a victim of its own success - as the town grew up around it the fort was engulfed, and eventually obliterated, by what is now Winnipeg.
Meanwhile the lower fort was used for a variety of things. Its main purpose was as a supply depot for the Red River settlement and the surrounding Indian and Métis population. The post traded essential manufactured goods to the farmers and hunters for produce that was in turn used for provisioning company treks into the north. The fort included several industrial buildings, such as a flour mill, sawmill, forge, and a brewery.
Every now and then there was a crisis that called for military action, and Lower Fort Garry was the obvious choice for a base of operations. In the 1840s, British troops were sent to the fort when a dispute erupted with the Americans over the boundary between Oregon and what is now British Columbia. When the Red River Rebellion broke out in 1870, Louis Riel occupied Upper Fort Garry, and the Canadian militia took the lower fort. Many of the North West Mounted Police of 1873-74 had been there already during the rebellion in 1870, including Inspector James F. MacLeod, who had met his fiancée, Mary Drever at Lower Fort Garry on the previous trip.
The first contingent of Mounties arrived in Lower Fort Garry on October 22, 1873, and on November 3 they were sworn in and commenced training. The bitter winter was spent drilling and learning to ride. The parade ground was frozen as hard as concrete, and was pretty unforgiving when a recruit was unexpectedly pitched from his horse. By the following June they were caught up in preparations for the arrival of Commissioner G.A. French and the other divisions, and headed out to meet them at Fort Dufferin. The fort was turned over once again to the militia.
The fort is now one of Parks Canada's flagship historic sites, but over the years it has also been a penitentiary, and insane asylum, a HBC residence and a country club. The HBC owned the fort until 1951, when it was given to the federal government.