The Calgary area was inhabited by pre-Clovis people whose presence has been traced back at least 11,000 years. The area has been inhabited by the Niitsitapi (Blackfoot Confederacy; Siksika, Kainai, Piikani), îyârhe Nakoda, the Tsuut'ina First Nations peoples and Métis Nation, Region 3.

As Mayor Naheed Nenshi (A'paistootsiipsii; Iitiya) describes, "There have always been people here. In Biblical times there were people here. For generations beyond number, people have come here to this land, drawn here by the water. They come here to hunt and fish; to trade; to live; to love; to have great victories; to taste bitter disappointment; but above all to engage in that very human act of building community."

In 1787, cartographer David Thompson spent the winter with a band of Peigan encamped along the Bow River. He was a Hudson's Bay Company trader and the first recorded European to visit the area. John Glenn was the first documented European settler in the Calgary area, in 1873.

In 1875, the site became a post of the North-West Mounted Police (now the Royal Canadian Mounted Police or RCMP). The NWMP detachment was assigned to protect the western plains from US whisky traders, and to protect the fur trade. Originally named Fort Brisebois, after NWMP officer Éphrem-A. Brisebois, it was renamed Fort Calgary in 1876 by Colonel James Macleod.

When the Canadian Pacific Railway reached the area in 1883, and a rail station was constructed, Calgary began to grow into an important commercial and agricultural centre. Over a century later, the Canadian Pacific Railway headquarters moved to Calgary from Montreal in 1996. Calgary was officially incorporated as a town in 1884, and elected its first mayor, George Murdoch. In 1894, it was incorporated as "The City of Calgary" in what was then the North-West Territories.[36] The Calgary Police Service was established in 1885 and assumed municipal, local duties from the NWMP.

The Calgary Fire of 1886 occurred on November 7, 1886. Fourteen buildings were destroyed with losses estimated at $103,200. Although no one was killed or injured,[38] city officials drafted a law requiring all large downtown buildings be built with Paskapoo sandstone, to prevent this from happening again.

After the arrival of the railway, the Dominion Government started leasing grazing land at minimal cost (up to 100,000 acres (400 km2) for one cent per acre per year). As a result of this policy, large ranching operations were established in the outlying country near Calgary. Already a transportation and distribution hub, Calgary quickly became the centre of Canada's cattle marketing and meatpacking industries.

By late 19th century, the Hudson's Bay Company (HBC) expanded into the interior and established posts along rivers that later developed into the modern cities of Winnipeg, Calgary and Edmonton. In 1884, the HBC established a sales shop in Calgary. HBC also built the first of the grand "original six" department stores in Calgary in 1913; others that followed are Edmonton, Vancouver, Victoria, Saskatoon, and Winnipeg