He was a fur brigade leader and explorer of the Columbia District and later became a U.S. citizen and an early settler of Oregon.
His first wife was Timmee T'Ikul Tchinouk, a Chinook woman, daughter of Chief Concomly and were married sometime before 1824 in the Oregon Territory.
[6][8] In 1811, Thomas McKay accompanied his father on the Tonquin to the mouth of the Columbia River, where the Pacific Fur Company's Fort Astoria was built.
Thomas, who was about 15 years old at the time, was at Fort Astoria when his father Alexander McKay was killed in late 1811 at Clayoquot Sound as the Tonquin was destroyed off of Vancouver Island.
In 1811 McLoughlin had married Marguerite Wadin, widow of Alexander MacKay and mother of Thomas McKay.
In 1828, McKay was in the party sent from Fort Vancouver to retrieve furs and property Indians took from Jedediah Smith on the Umpqua River in southern Oregon.
George Simpson, head of the HBC, had decided to try to over-exploit the Snake Country and create a "fur desert", for the political purpose of keeping American trappers and traders away.
McKay, along with other former NWC trappers such as Peter Ogden, Finan McDonald, Francois Payette, and others, "took up Simpson's orders with a fanatical zeal, declaring war on fur-bearing animals south of the Columbia," as historian Richard Mackie put it.
John Kirk Townsend, who was accompanying an American expedition to establish Fort Hall, described Thomas Mckay's party at the future site of Fort Hall in 1834 as consisting of 17 French Canadians and "half-breeds", and 13 Indians (Nez Perce, Chinook, and Cayuse).
Townsend also noted that McKay enforced the HBC policies brigade order, decorum, and strict subordination, as well as the prohibition of trading whiskey to the Indians.
All these things, Townsend noted, were in stark contrast to the behavior of American fur traders in the region.
[10] Fort Hall was part of an effort by Nathaniel Jarvis Wyeth to break into the Columbia region and compete with the HBC.
Politically the entire Oregon Country was free and open to British and American ventures, but the HBC was able to maintain its dominance in the region through various barriers to entry tactics such as dumping and predatory pricing.