Alex R. Macdonell joined the NWMP in 1876, and was an inspector stationed at Wood Mountain near the international border. His duties included investigating horse stealing west of Manitoba, and patrolling a wide area around the Wood Mountain post. He was active during Sitting Bull's time in Canada, and helped negotiate the chief's return to American soil. On September 15, 1885 he was promoted to the rank of Superintendent, and went on to have command of "K" division at Battleford. The "K" division left Battleford for Lethbridge in May of 1887, and Macdonell was granted a leave of absence in this year to marry. He returned to Lethbridge after his leave, and in his reports strongly recommended the adoption of some type of felt hat for Prairie NWMP officers' uniforms. In 1888, Macdonell assumed command of "H" division (Macleod and detachments), reporting to District Superintendent, Sam Steele. Official police reports indicate he was in this post until at least 1893, and retired from the force in 1895.Subsequent diary entries suggest he ranched and farmed in Alberta after retiring from the NWMP. He and Sam Steele and other partners had shared mining interests in the Kootenay district of British Columbia, and Alex passed away in 190[7]. Superintendent Macdonell’s wife Min was Marie Harwood’s aunt, and it was while visiting her aunt in Fort Macleod that Marie first met Sam in 1889.

There is further discussion of 'Lex' in Marie Steele's letters to Sam; A.R. Macdonell had once proposed marriage to her, although married Marie's aunt Min.