Born in Scotland, John Macdonell came to New York in 1773. Commissioned as an ensign in the Royal Highland Emigrants (84th Regiment) in June 1775 and later transferred to Butler's Rangers, he served with distinction until 1784, when he settled with his clansmen in Charlottenburg Township. He represented Glengarry in the Legislative Assembly from 1792 to 1800 and was chosen as its first speaker from 1792 to 1796. Macdonell also served as Lieutenant of Glengarry from 1793 to 1808, commander of the 2nd Battalion Royal Canadian Volunteers from 1796 to 1802, and paymaster of the 10th Royal Veteran Battalion from 1807 until his death.