In Canada, copyright protection normally lasts until 50 years after the author's death (50 years p.m.a.) since 1999. However, under the old Copyright Act, photographs were protected only for 50 years after their creation. When Bill C-32: An Act to Amend the Copyright Act came into effect on January 1, 1999, photographs whose copyright already had expired remained in the public domain. As a result, Canadian photographs taken before January 1, 1949 and not under Crown copyright are in the public domain in Canada. See also [1] at the bottom.
Such images may be tagged using {{PD-Canada}}, which populates this category. Note that one also has to determine whether an image so tagged also is in the public domain in the U.S.