Canada's History magazine has the highest readers-per-copy of any magazine published in Canada, at 23.7 readers per copy, according to PMB. Not far short of a million adult (well, over 12) readers per issue, if these figures are credible.
Come to think of it, I did meet someone recently, in a non-historical, non-blog related context, who said out of the blue, I see your column in Canada's History. So it must be true.
H/T Canadian Magazines Blog