"Native Americans were a much more important ignition source than lightning throughout the eastern USA, except for the extreme Southeast."
http://journals.sagepub.com/doi/10.1177/0959683608095581
Indians created the prairies, too:
"most ecologists now believe that the eastern prairies "would have mostly disappeared if it had not been for the nearly annual burning of these grasslands by the North American Indians," during the last 5,000 years. A case in point is the nineteenth-century invasion of many grasslands by forests after fire had been suppressed in Wisconsin, Illinois, Kansas, Nebraska, and elsewhere"
http://jan.ucc.nau.edu/~alcoze/for398/class/pristinemyth.html
They also had cities, farmed and bred crops...
