William McKay (1772 – 18 August 1832) was a noted trader and traveler in Upper Canada, who subsequently served as a military officer during the War of 1812.
William was actually born along the Mohawk River valley, where his father, Donald, had settled after being discharged from the British Army. After the American War of Independence, Donald, who was a United Empire Loyalist, migrated to Canada, eventually setting the family in Glengarry district.
William joined the North West Fur Company as a voyageur and fur trader in about 1790, and travelled widely in the regions north and west of the Great Lakes. He became a partner in the company in 1796 and retired from it in 1807.
When war broke out with the United States of America, McKay almost immediately offered his services to the British army. His first major contribution was to make a journey of 500 miles (800 km) by canoe from Montreal to the British military post on St. Joseph Island on Lake Huron via York, the provincial capital, in only eight days. The news of the declaration of war he carried, along with orders from Major General Isaac Brock, the Commander in Upper Canada, allowed the British detachment to take the American detachment at Fort Mackinac by surprise. This victory encouraged many Native Americans to side with the British, resulting in further British victories in the west during the following year.
Later during the autumn and winter of 1812, McKay returned to Montreal to help raise the Canadian Voyageurs, a corps which transported supplies to Upper Canada. When this corps was transferred to the Commissariat, McKay became an officer in the Select Embodied Militia. During 1813, McKay was promoted to Major and given command of the Michigan Fencibles, a local quasi-regular unit recruited in the North West.
Early in 1814, the Americans had captured the isolated post of Prairie du Chien. This threatened the morale and allegiance of the Indians. Supported by the newly-appointed Commander at Fort Mackinac, Lieutenant Colonel Robert McDouall, McKay (who now held the local rank of Lieutenant Colonel) mounted a scratch expedition of Fencibles, voyageurs and Indians which recaptured the post at the Siege of Prairie du Chien.
McKay was later appointed to head the Indian Department at Mackinac. When the war ended, he (and McDouall) opposed returning Mackinac and Prairie du Chien to the Americans, as it would place many Indians at their mercy, but was overruled.
McKay died of cholera in 1832. He was married, with one son.