The name "Rocky Mountain Rangers" first emerged in 1885 as the name taken by a militia of one hundred and fourteen men from British Columbia and Alberta who joined to fight in the Northwest Rebellion. The rebellion itself was the culmination of tensions between the Metis and the white population in the Red River area of Manitoba . The tensions were caused in part by white settlers displacing the Metis who had settled in the Red River Valley after Confederation, and also by the fact that the Canadian Government denied the Metis' legal rights. The Northwest Rebellion of 1885 was led by Louis Riel, the Metis leader who returned to Canada from his home in Montana to fight for what he saw as the Metis' right to national self-determination. Although activity during the Rebellion was further east, Alberta residents had reason to fear that the fighting would spread to their province in the form of an alliance of the Cree and Blackfeet tribes against the white settlers.

In 1885 Hon. A.P. Caron, Minister of Militia and Defense, authorized Captain John Stewart to raise four troops of the Rocky Mountain Rangers. Although three of the troops were renamed and put under different leadership, the troop raised by Captain Stewart at Fort Macleod, Alberta retained the name Rocky Mountain Rangers. The Rangers' three duties during the rebellion were "�to guard the 200-mile frontier between Lethbridge and the Cypress Hills; protect the cattle herds from thieves and rustlers; and act as a buffer to keep warlike American Indians from surging north to join their Canadian cousins." General Order No. 3 stated that a unit named the Rocky Mountain Rangers would be raised for actual service under Captain Stewart.

The majority of the troops in the 1885 Rocky Mountain Rangers were cowboys, ranchers and ex-Mounties. Although they did not have the appearance of a typical military unit, the Rangers' expertise and knowledge regarding firearms, Indians and the Canadian west rendered their services invaluable. One notable member of the 1885 Rocky Mountain Rangers was the hunter, explorer and guide John George Brown, otherwise known as "Kootenai" Brown. Kootenai took his name from his great appreciation of the Waterton (Kootenay) lakes in British Columbia . Upon learning about the situation in the Northwest, Kootenai traveled to Fort Macleod and immediately signed up with the Rangers as their chief guide and scout. It can be assumed that the flamboyant Kootenai Brown was right at home with the Rangers. "Kootenai, in his buckskin shirt, his wide slouch hat, his knife and rifle, and the natural ease with which he sat in a saddle added his own particular touch to what was already a colorful group of men." On 29th April, 1885 the Rocky Mountain Rangers, along with Kootenai Brown rode east from Fort Macleod.

The main function of the 1885 Rocky Mountain Rangers was to guard the district around Cypress Hills. As events progressed it became apparent that the Rangers in Alberta would not be participating in as much of the Rebellion as perhaps the troops would have liked. However, two notable incidents did occur. The first was on 19th May when a man herding cattle in the Medicine Hat area was attacked by Natives and half-breeds, and the second incident occurred in early June when a patrol near Cypress Hills was attacked. Thus, "While the threat of trouble might have been present, to most of the action-loving cowboys the daily patrols were a chore." The 1885 Rocky Mountain Rangers were never able to participate in full battle during the Northwest Rebellion.

The 1885 Rocky Mountain Rangers were disbanded on 17th July that year. There was probably much disappointment among the troops at the disbanding of the corps. However, Captain Stewart was able to obtain the Riel Rebellion medal and the Rebellion scrip. The scrip entitled any Ranger who applied for it either eighty dollars or three hundred and twenty acres of land.

When examining the brief experiences of the 1885 Rocky Mountain Rangers it is important to note that there is no connection between this militia and the Rocky Mountain Rangers regiment created in 1898 and existing into the present in Kamloops , British Columbia . The connection is in name only. Perhaps this is because of the romantic associations of the Rangers' name with a group of tough cowboys determined to protect the land below the Rocky Mountain foothills. The 1885 Rocky Mountain Rangers are perpetuated by the South Alberta Light Horse in Medicine Hat , Alberta.