The "Biographical Dictionary of the Nor'Westers", published as part of his Documents Relating to the North West Company (1934), is full of evidence of the extensive correspondence he carried on with descendants of the partners, trying to locate new letters, journals and account books.

Although articles in the Dictionary of Canadian Biography have expanded knowledge of some of the Company's partners, Wallace's work remains a fundamental source.

This collection of manuscripts was a key source for Elaine A. Mitchell's Fort Temiskaming and the Fur Trade (1977, University of Toronto Press).

The Reverend William George Wallace MA DD was part of the officers of the inaugural general council in Toronto in June 1925 for the United Church.

During the First World War, he reached the rank of major in the Canadian Expeditionary Force (1915 – 1918), serving overseas, and involved in the Khaki College as the commanding officer.