I can believe that Indiana used to be totally wooded. There are still some fairly wide areas in the southern half of the state (Brown County, Morgan-Monroe, etc.) that are pretty densely forested.
Conversely, New Hampshire used to be pretty much totally defoliated, farmland as far as the eye could see. Mostly pines, too. Then when the Industrial Revolution came everyone abandoned their farms (the soil is pretty poor and rocky up there anyway) and moved to the cities, and the land changed into the gorgeous diciduous forests now famous for fall leaf peeping! It's pretty cool, you can walk waaaaaaayyyyy back into the woods and there will always be these random stone walls crisscrossing the land.