Born in Ennistymon, Ireland and educated at Eton and Oxford, Brown was commissioned as a British Army officer in 1857 "without purchase" (a reference to the practise then common of wealthy Britons purchasing officers' commissions), joining the 8th Regiment as an ensign
After serving in India in 1858 and 1859, in 1862 he sold his commission and joined the flood of prospectors joining the Cariboo Gold Rush. He proved unsuccessful as a prospector, turning to trapping and then briefly policing, serving as constable in Wild Horse Creek, BC (now gone).
After a quarrel (and obligatory gunfight) at Fort Benton, Montana, with "celebrated hunter" Louis Ell, in which Ell was killed, and subsequent trial and acquittal by a territorial jury, Brown returned to his beloved Kootenay, where he settled, building a reputation as a guide and packer.
Always arguing vigorously for the region's preservation, after the Kootenay Forest Reserve (a Canadian version of a national forest) was established in 1895,Brown became a fishery officer and in 1910, a forest ranger.
He died at Waterton Lakes, Alberta.
- Morrison, Elsie (1950). Calgary, 1875-1950 : A souvenir of Calgary's seventy-fifth anniversary. Calgary: Calgary Publishing Co. p. 33.
- Rodney, William. "Brown, John George, 'Kootenai'", in The Canadian Encyclopedia (Edmonton: Hurtig Publishing, 1988), Volume 1, p.289.
- Marsh, James H. (1988). "Brown, John George, 'Kootenai'". The Canadian Encyclopedia, Volume 1 (Edmonton: Hurtig Publishing). pp. p. 289. ISBN 0-88830-326-2.