The ground surface temperature histories of the past 500 years were reconstructed at 10 sites in northern Ontario and Quebec. The regions experienced a warming of ~1–2 K for the past 150 years, agreeing with borehole reconstructions for southern Ontario and Quebec and proxy data. Permafrost maps locate the sites in a region of discontinuous permafrost but our reconstructions suggest that the potential for permafrost was minimal to absent over the past 500 years.