Gilbert Malcolm Sproat was born in Kirkcudbright, Scotland and came to Vancouver Island in 1860 as a representative of the London-based speculative enterprise called Anderson, Anderson and Company which was financing a sawmill at the head of Alberni Canal. Sproat became resident manager of the mill, owned by Captain Edward Stamp. Sproat and Stamp negotiated with Governor James Douglas for land and timber rights for the mill.

The mill operated from 1861-1865. In 1863, when Sproat became manager, as many as ten vessels at one time were loading lumber and spars for shipment to Australia, China, and South America, as well as Victoria.

After the mill closed in 1865, Sproat returned to England. He was an amateur anthropologist and had taken an interst in Vancouver Island's First Nations. In 1868 he published a volume entitled Scenes and Studies of Savage Life, based on his observations.  In 1872 he became British Columbia's first Agent-General in London. In 1876, he came back to BC and was appointed Indian Land Commissioner to determine the location and size of Indian reserves. He was magistrate and Gold Commissioner in the West Kootenays from 1885 to 1890, and, after leaving government service, was active in land development in Revelstoke, Nelson, and other mining towns. He returned to Victoria in 1913 and died there the same year.

In 1863 Dr. Robert Brown of the Vancouver Island Exploring Expedition renamed Sproat Lake after Gilbert Malcolm Sproat because Sproat had arranged transportation for Brown's party aboard his sawmill's schooner. Brown was unaware the lake had been known previously by its anglicized Nuu-chah-nulth name, Kleecoot.