In September 1892, however, Stimson was a member of the first non-Indian party to climb Ninaistákis. At its summit, they discovered evidence of the mountain's long history of ceremonial use. On terrain far too rugged for bison to traverse, three bison skulls were found, two of which were so old "that the black sheaths of their horns had been worn away by winds and storms, and the sheaths of the other horns had turned from black to yellowish white."