Ancestry. There are 8.8million people included in the record set.
Among them are more than 1million people born in Ireland and more than 2million whose parents were born in Ireland, so this is a hugely important release not just for Canadians but for anyone with Irish emigrants in their family tree.
It was the 6th census of Canada and it was taken on 1 June 1921.
The Census is free to view on Ancestry.ca (you have to register with your email and a user name, but there's no requirement for financial information to be provided).