The Canadian government formed the North-West Mounted Police (NWMP) in 1873 to secure and control the vast North-West Territories, corresponding to present-day Saskatchewan and Alberta, and much of what is now Manitoba. Fort Macleod, the first NWMP post in Alberta, was established in 1874, followed by Fort Calgary in 1875. The primary duties of the Mounted Police were to establish friendly relations with the First Nations, eradicate the whisky trade, and maintain law and order.

A unique institution, the force was a combination of the military, the police, and minor judiciary. Consequently, its routine duties were quite diverse. "Mounties" delivered the mail, provided medical services and relief supplies, took the census, collected customs duties, established meteorological records, and reported livestock and crop conditions. Moreover, they helped to supervise local Native affairs, and functioned as justices of the peace, trying their apprehended suspects. In short, the Mounted Police were a crucial part of the federal administration of prairie Canada.

Because their mandate included the supervision of civil as well as criminal matters, their broad duties kept the police in touch with nearly every aspect of frontier life. They quickly became knowledgeable in a wide range of subjects, from the quality of export cattle to the sundry remedies for fevers. Their regular reports included valuable information for Ottawa. During their routine circuits through the region, they were often the only source of aid or information in sparsely populated areas. Consequently, they were important to the process of integrating new immigrants into Canadian society.

A number of officers of the force came from elite Eastern Canadian backgrounds, were well educated and had military experience. As representatives of the upper strata of Canadian society, they brought with them fixed ideas of proper cultural and social norms. These ideas influenced not only their social expectations but also their perceptions of crime. Since their predominant duty was to maintain order on the frontier, the police had to differentiate between crimes that were merely a nuisance, and those that were a threat to social stability. The distinctions they made were often based on assumptions about the social order, in which less was expected of the "lower classes".

The police were closely linked to another elite group, the cattlemen. More often than not, the two groups shared a common background, heritage, and world-view. Even without these commonalties, the police and ranchers were tied to a mutual interest in the cattle business. Protecting ranchers against cattle theft, illegal branding, and related stock crimes was one of their primary duties. Ranchers were quick to repay this service with unwavering support of the police. Close, personal relationships developed between the police and ranchers through frequent contact. In some cases, police outposts were positioned on ranch properties. Finally, many members of the force saw the economic opportunities ranching afforded, and became ranchers themselves once they completed their terms of duty.

Whether by virtue of their intrinsic standing, their entry into the cattle kingdom, or their participation in local affairs, the police were a fundamental feature of the development of Calgary and southern Alberta. In 1920, the title of the force was changed to the Royal Canadian Mounted Police (RCMP) and its duty was to enforce federal legislation. The RCMP later assumed provincial duties as well.