The Collaborative International Dictionary of English v.0.48:

whitehorse \white"horse\
   a whitecap[2] (the wave).
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Whitehorse
    n 1: the provincial capital of the Yukon Territory

U.S. Gazetteer Places (2000):

Whitehorse, SD -- U.S. Census Designated Place in South Dakota
   Population (2000):    141
   Housing Units (2000): 43
   Land area (2000):     2.673014 sq. miles (6.923073 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.673014 sq. miles (6.923073 sq. km)
   FIPS code:            71140
   Located within:       South Dakota (SD), FIPS 46
   Location:             45.271141 N, 100.887494 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Whitehorse, SD
    Whitehorse