"Over an irregular tract of gently rolling sandy hills, perhaps about three quarters of a mile square, were scattered several hundred detached and isolated buttes or cliffs of sandstone, each butte from fifteen to fifty feet high, and from thirty to a couple of hundred feet across. Some of them rose as sharp peaks or ridges, or as connected chains, but much the greater number had flat tops like little table-lands. The sides were perfectly perpendicular, and were cut and channelled by the weather into the most extraordinary forms; caves, columns, battlements, spires, and flying buttresses were mingled in the strangest confusion. Many of the caves were worn clear through the buttes, and they were at every height in the sides, while ledges ran across the faces, and shoulders and columns jutted out from the corners. On the tops and at the bases of most of the cliffs grew pine trees, some of considerable height, and the sand gave every thing a clean, white look.
Altogether it was as fantastically beautiful a place as I have ever seen: it seemed impossible that the hand of man should not have had something to do with its formation. " -Theodore Roosevelt, Hunting Trips of a Ranchman.

http://fwp.mt.gov/mtoutdoors/HTML/articles/2005/medicinerocks.htm