The Collaborative International Dictionary of English v.0.48:

Hackmatack \Hack"ma*tack`\ (h[a^]k"m[.a]*t[a^]k`), n. [Of
   American Indian origin.] (Bot.)
   The American larch (Larix Americana), a coniferous tree
   with slender deciduous leaves; also, its heavy, close-grained
   timber. Called also tamarack.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tamarack \Tam"a*rack\, n. (Bot.)
   (a) The American larch; also, the larch of Oregon and British
       Columbia (Larix occidentalis). See Hackmatack, and
       Larch.
   (b) The black pine (Pinus Murrayana) of Alaska, California,
       etc. It is a small tree with fine-grained wood.
       [1913 Webster]

WordNet (r) 3.0 (2006):

tamarack
    n 1: medium-sized larch of Canada and northern United States
         including Alaska having a broad conic crown and rust-brown
         scaly bark [syn: American larch, tamarack, black
         larch, Larix laricina]

U.S. Gazetteer Places (2000):

Tamarack, MN -- U.S. city in Minnesota
   Population (2000):    59
   Housing Units (2000): 48
   Land area (2000):     3.598216 sq. miles (9.319337 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    3.598216 sq. miles (9.319337 sq. km)
   FIPS code:            64156
   Located within:       Minnesota (MN), FIPS 27
   Location:             46.647713 N, 93.126321 W
   ZIP Codes (1990):     55787
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Tamarack, MN
    Tamarack