The Collaborative International Dictionary of English v.0.48:

Rockaway \Rock"a*way\, [Probably from Rockaway beach, where it
   was used.]
   Formerly, a light, low, four-wheeled carriage, with standing
   top, open at the sides, but having waterproof curtains which
   could be let down when occasion required; now, a somewhat
   similar, but heavier, carriage, inclosed, except in front,
   and having a door at each side.
   [1913 Webster] Rockelay

U.S. Gazetteer Places (2000):

Rockaway, NJ -- U.S. borough in New Jersey
   Population (2000):    6473
   Housing Units (2000): 2491
   Land area (2000):     2.088806 sq. miles (5.409983 sq. km)
   Water area (2000):    0.017358 sq. miles (0.044956 sq. km)
   Total area (2000):    2.106164 sq. miles (5.454939 sq. km)
   FIPS code:            64050
   Located within:       New Jersey (NJ), FIPS 34
   Location:             40.900365 N, 74.513557 W
   ZIP Codes (1990):     07866
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Rockaway, NJ
    Rockaway