The Black Hills are a magnificent outcrop of mountains in the heart of the great plains.  Spearfish on the north end of the Black Hills, routinely records high winds (though not technically chinooks, the rip!) and some of the largest temperature swings on earth (as a result).   They are an oasis of temperate forest in an otherwise expansive completely grassy steppe environment.   Understandably they were immensely sacred to the natives that lived in the area.   The mistique of the black hills seems to have loomed even larger than their reality, unbelievable.  They are not really black, and they most definitely don't contain gold "from the grassroots, down" , happily.   The geologic history is far more interesting than even the varied, rolling terrain might lead you to believe.