He was born in Inverness, Scotland, in 1812, and by 1833 moved to the Pacific Northwest in the service of the Hudson's Bay Company (HBC).

Tolmie's journal entry about it is the first recorded eyewitness description of an earthquake in the Puget Sound region.

In August 1833 he arranged a "botanizing excursion" to the mountain, with Lachalet, a Nisqually, and Nuckalkat, a Puyallup, as guides.

Wanting to reach the snow level, Tolmie chose the nearest snowy peak and climbed it with Lachalet and Nuckalkat.

[7] Due to this trip, Dr. Tolmie was the first European to explore the Puyallup River valley and Mount Rainier.

As a result of this crisis of conscience, he took a leave of absence to London and France, where he did postgraduate courses for two years.

In 1835, Dr. Tolmie spent 10 days with area natives, and with their help, discovered high-quality coal which, before the opening of mines soon after, needed to be imported from Britain.

[10] When he returned in 1843 he decided to relocate the fort closer to the Edmond Marsh and Sequalitchew creek in order to have better access to fresh water.

He worked to achieve good relationships with the region's Native Americans and the growing number of United States settlers.

[12] In 1846 Tolmie served as a legislator in the Provisional Legislature of Oregon representing Lewis County and HBC interests.

[13][14] In 1857, Dr. Tolmie supported Chief Leschi, who was being tried for murders related to the Puget Sound War of 1855-1856.

[15] Dr. Tolmie was credited with saving the American Puget Sound settlement from a war among the natives.

"[8] Another testimonial, printed in the Victoria Daily Standard stated, "Dr. Tolmie did much to mollify savage dispositions by his able management of the Indians some quarter of a century, thus paving the way for peaceful occupation of the west.

[17] In 1859 the Hudson's Bay Company transferred Tolmie to Fort Victoria on Vancouver Island.