From the Rocky Mountain Research Station:
When the words to the classic folk song “Home on the Range” were written in 1872, U.S. rangelands were much more extensive than they are today. Over the past three centuries in the coterminous United States, one-third of rangelands — once covering a billion acres — have been modified or converted to other land uses. This shift is projected to continue, because privately owned rangelands, which are the most likely to be converted to other uses, represent more than 60 percent of America’s rangelands.
Read the original research here.