David Thompson was born in 1770 in London, England. He was educated at a school for orphans and at 13 was apprenticed to the Hudson's Bay Co. With the HBC, Thompson was trained as a trader and surveyor. But since he had little hope of advancement or being able to fulfill his dream to become an explorer, he left the HBC in 1797 and joined the North West Co. 

In his first year with the NWC, he traveled some 2,000 miles, fixing the positions of the company posts in Manitoba, the Dakotas and Minnesota. Also in that year, he became the first European to find the headwaters of the Mississippi.

From 1807 to 1812, Thompson lived his dream of being an explorer and fur trader. He helped to establish numerous NWC posts, all the way from Lake Windermere on the headwaters of the Columbia River in B.C. to Montana and Idaho in the US. Thompson also carried furs from BC across the prairies and mapped much of southern BC in the process. During the winter of 1810 Thompson, led by a First Nations guide, trvavelled through deep snow by way of the Upper Athabasca River and came across Athabasca Pass. Later this route became the main route through the mountains for British traders.

On many of his travels Thompson was accompanied by his First Nations wife, Charlotte, daughter of Irish-born trader Patrick Small and his native wife. The first of their 13 children was born at Rocky Mountain House.

In 1811 Thompson completed his survey of the Columbia River to the Pacific Ocean and the following year he left the NWC and returned to Eastern Canada to complete his now famous map of Western Canada which identified the first practical route across the continent. He and Charlote purchased a farm aat Williamstown, Glengarry County, Upper Canada (now Ontario) in 1815. Thompson did not receive recognition for his work and was forced to work as a surveyor to augment his meagre finances. He died in poverty near Montreal in 1857 and is buried in Mount Royal Cemetery. His house in Williamstown, Ontario has been preserved a sa heritage site.