Wordnet 3.0
NOUN (2)
1. 
 mountains in southwestern South Dakota and northeastern Wyoming; 
 sacred to the Sioux (whites settling in the Black Hills led to the Battle of Little Bighorn); 
 site of Mount Rushmore; 
2. 
 mountains in western South Dakota and northeastern Wyoming; 
WordNet (r) 3.0 (2006):
Black Hills
    n 1: mountains in southwestern South Dakota and northeastern
         Wyoming; sacred to the Sioux (whites settling in the Black
         Hills led to the Battle of Little Bighorn); site of Mount
         Rushmore
    2: mountains in western South Dakota and northeastern Wyoming