Henry Kelsey is credited with being the first white man to travel the western plains of Canada, 1690 -92. He was apprenticed to the Hudson Bay Company in 1684 and served the company nearly 40 years - all but 3 of them at Hudson Bay.
Canada Post Office issued a stamp honouring Henry Kelsey on April 15, 1970.

National Archives of Canada
First Day Covers
Canada Post Office Publicity First Day Cover

Shering


Canada Envelope Company


Jackson

Overseas Mailers

H and E

Cole Cover

Artopages

David Pritchard

Elliot Marion


Ayerst Laboratories


Rosecraft


Usages
Domestic letter

Toronto local mail, May 6, 1970
6 cents domestic letter rate