Charles Goodnight and Oliver Loving are whom you speaking about Richard. In the museum in Canyon, Texas there is much about the two, especially Charles Goodnight. He was a salty individual indeed, and not to be messed with. He virtually STARTED cattle ranching in the Texas Panhandle,and was before, and from time to time a Ranger.
Mr. McMurtry did not plagiarize a book, he plagiarized a LIFE. Every where you go in the Texas Panhandle you will see Goodnight mark on the history there. He is even in the sequel to Lonesome Dove, called "Dead Man's Walk".