What year did Canada celebrate the first Thanksgiving?

Not pilgrims, there weren't any of those in Canada. Canadian Thanksgiving like similar ceremonies worldwide celebrates a successful harvest. It was probably first celebrated as a Harvest Home celebration the first time settlers successfully brought in a crop. It was not an official holiday until 1957, but Harvest Homes were a well-established custom long before then. American immigrants even brought with them some of the American customs, particularly the eating of turkey.