[eemy]

That would be Anticosti Island.

I find that smaller scale images tend to give a pretty good sense of the region. The river pattern and topography excluded the west coast, and didn't really seem consistent with the Canadian Shield either. The lack of population suggested the northern part of the prairies, but the type of blue on the water excluded inland lakes except the Great Lakes (a bit of a cheat there I suppose), which I knew it wasn't a part of. That left the east coast. The orientation of the coast line immediately eliminated most parts of the east cost, and it was a matter of checking a few locations that seemed to share that orientation.

Hopefully I have a stumper coming up.