The Collaborative International Dictionary of English v.0.48:

Silver State \Silver State\
   Nevada; -- a nickname alluding to its silver mines.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Silver State
    n 1: a state in the southwestern United States [syn: Nevada,
         Silver State, Battle Born State, Sagebrush State,
         NV]