How did anyone settlers or Indians survive the icy Maine winters before the invention of the indoor furnace?

The Indians of the Northeast kept everything pretty simple. They Summered at the coasts, and Wintered inland (typicaly in Fur Forestation). They built shelters of Wood, bark, Pine Straw, deer hide, etc. Many housed several families at a time. As for more ancient civilizations in the Northeast,evidence of more ancient retreats exist in the inland forests by the presence of "cairns". Some are still erect man-made caves of stone, others destroyed to just mounds of stone. They are present accross the northern northeast states. source: the web