Thomas Douglas was born into an aristocratic Scottish family, the seventh son of Dunbar Douglas, 4th Earl of Selkirk. His upbringing on the family estate exposed him to the social and economic hardships faced by Scottish Highlanders.

Selkirk enrolled at the University of Edinburgh, immersing himself in the intellectual ferment of the Scottish Enlightenment. His studies included law and philosophy, shaping his later philanthropic and colonial ideas.

The unexpected deaths of his older brothers left Thomas as the 5th Earl of Selkirk. This inheritance provided him with the substantial wealth and title necessary to pursue his ambitious colonization schemes.

Selkirk traveled extensively through the Highlands, observing firsthand the displacement of tenant farmers during the Highland Clearances. This experience cemented his resolve to find new lands for displaced Highlanders.

Selkirk published his influential pamphlet analyzing the causes and consequences of Highland emigration. It argued for organized settlement in British North America as a solution to social dislocation in Scotland.

After failed proposals to the government, Selkirk used his own funds to establish a settlement of 800 Scottish emigrants on Prince Edward Island. This was his first practical test of colonization theory.

Selkirk established a second settlement at Baldoon in present-day southwestern Ontario. The project faced significant difficulties including disease and poor land, demonstrating the challenges of frontier colonization.

Selkirk married Jean Wedderburn-Colvile, daughter of a powerful Scottish merchant family with connections to the Hudson's Bay Company. This marriage provided crucial financial and political support for his future ventures.

Leveraging his wife's family connections and his own wealth, Selkirk acquired a substantial shareholding in the HBC. This gave him the influence to pursue a settlement project in the company's vast territorial grant.

Selkirk received a grant of 116,000 square miles (300,000 km²) from the HBC, known as Assiniboia, in present-day Manitoba and the Dakotas. The grant was intended to create an agricultural settlement to supply the fur trade.

The first party of settlers, primarily from Scotland and Ireland, arrived at the junction of the Red and Assiniboine Rivers. They built Fort Douglas and began farming, founding what would become Winnipeg, Manitoba.

To secure food for his colony, Selkirk's governor banned the export of pemmican from the district. This directly challenged the North West Company's supply lines, triggering violent conflict in the fur trade wars.

Métis and North West Company forces clashed with colony settlers, killing 21 including the governor. The colony was temporarily abandoned, marking the lowest point in Selkirk's colonization efforts.

Selkirk traveled to North America, recruiting Swiss mercenaries to escort settlers back to Red River. He seized Fort William from the NWC and re-established colonial authority, though this led to legal repercussions.

Selkirk concluded a treaty with the Cree and Saulteaux (Ojibwe) nations, exchanging annual payments for land rights in the colony area. This was one of the first treaties in western Canada preceding later Numbered Treaties.

Selkirk was embroiled in costly lawsuits brought by the North West Company for his seizure of Fort William. The legal expenses, combined with the colony's costs, began to devastate his personal fortune.

In ill health from tuberculosis, Selkirk left North America for the last time. The Red River Colony, though diminished, had been re-established and would survive to become the nucleus of Manitoba.

From his sickbed, Selkirk wrote and published this detailed justification of his colonization project and his conflict with the NWC. It remains a key primary source for understanding the fur trade wars.

Lord Selkirk died in exile in southern France, financially depleted and his health broken. Despite his death, the Red River Colony endured, fundamentally shaping the demographic and political future of Western Canada.