"The Black Hills of South Dakota are not hills. Hills rise less than 1.000 from the surrounding area, while mountains rise above that height. The Black Hills rise from 2,000 to 4,000 feet above the surrounding area. Several peaks exceed 6,000 feet, and the highest "hill," Harney Peak, reaches 7,242 feet, higher than any peak in the Appalachian or Ozark mountains. The Sioux Indians named the mountains Paha Sapa ("hills of black") because from the plains, pine trees covering the mountains appear black (and because the Sioux had no idea geologists strictly distinguished between hills and mountains)."
These CTPB facts come from the book "Contrary To Popular Belief" by Joey Green and are not my own words.