How did Buffalo Gap get its name as noted in the book, On the Rez?

Located fifteen miles west of the reservation line, Buffalo Gap, SD is a small town named for the gap in the Black Hills that the Sioux used to enter and leave the Black Hills. It has been the site of many battles, and it was one of the wildest Western towns ever. The town was used as a terminus and departure point for the gold mines in the Hills around 1885, but it diminished when the railroad extended to Rapid City. Buffalo Gap was also the site of the murder of Wesley Bad Heart Bull.