I think the furthest north you can drive is probably Whitehorse in Yukon [EDIT: not BC] on the Pan-American Highway. But presumably you were looking at the eastern end of Canada.
[ADDED: As someone else noted, you can keep going north of Whitehorse with the Pan-American Highway eventually crossing the border with Alaska or the Dempsey Highway.]
[ADDED: As someone else noted, you can keep going north of Whitehorse with the Pan-American Highway eventually crossing the border with Alaska or the Dempsey Highway.]