According to the research done by Charles Mann in 1491, the indigenous population used fire to drive prey into hunting zones. I believe he even presents the theory that is what created the grassland plains across the central US. He presents quite a bit of evidence from primary sources.
I’m not a historical scholar and so maybe his evidence is “bunk”, but his work seems to be very well received in academic circles (unlike say Graham Hitchcock who is seen as more of a Malcolm Gladwell type).
Most of the area in between the Mississippi and the west coast doesn’t get enough precipitation to support trees. I don’t think that was generally understood until Powell’s survey a couple hundred years later.
I’m not a historical scholar and so maybe his evidence is “bunk”, but his work seems to be very well received in academic circles (unlike say Graham Hitchcock who is seen as more of a Malcolm Gladwell type).