The Collaborative International Dictionary of English v.0.48:

El Dorado \El` Do*ra"do\, pl. El Doradoes. [Sp., lit., the
   gilt (sc. land); el the + dorado gilt, p. p. of dorare to
   gild. Cf. Dorado.]
   1. A name given by the Spaniards in the 16th century to an
      imaginary country in the interior of South America,
      reputed to abound in gold and precious stones.
      [1913 Webster]

   2. Any region of fabulous wealth; exceeding richness.
      [1913 Webster]

            The whole comedy is a sort of El Dorado of wit. --T.
                                                  Moore.
      [1913 Webster]

WordNet (r) 3.0 (2006):

El Dorado
    n 1: an imaginary place of great wealth and opportunity; sought
         in South America by 16th-century explorers [syn: El
         Dorado, eldorado]

U.S. Gazetteer Counties (2000):

El Dorado -- U.S. County in California
   Population (2000):    156299
   Housing Units (2000): 71278
   Land area (2000):     1710.847027 sq. miles (4431.073269 sq. km)
   Water area (2000):    77.249587 sq. miles (200.075503 sq. km)
   Total area (2000):    1788.096614 sq. miles (4631.148772 sq. km)
   Located within:       California (CA), FIPS 06
   Location:             38.768651 N, 120.571902 W
   Headwords:
    El Dorado
    El Dorado, CA
    El Dorado County
    El Dorado County, CA


U.S. Gazetteer Places (2000):

El Dorado, AR -- U.S. city in Arkansas
   Population (2000):    21530
   Housing Units (2000): 9891
   Land area (2000):     16.269927 sq. miles (42.138915 sq. km)
   Water area (2000):    0.052032 sq. miles (0.134761 sq. km)
   Total area (2000):    16.321959 sq. miles (42.273676 sq. km)
   FIPS code:            21070
   Located within:       Arkansas (AR), FIPS 05
   Location:             33.213521 N, 92.662553 W
   ZIP Codes (1990):     71730
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    El Dorado, AR
    El Dorado


U.S. Gazetteer Places (2000):

El Dorado, KS -- U.S. city in Kansas
   Population (2000):    12057
   Housing Units (2000): 5460
   Land area (2000):     6.365517 sq. miles (16.486613 sq. km)
   Water area (2000):    0.057597 sq. miles (0.149176 sq. km)
   Total area (2000):    6.423114 sq. miles (16.635789 sq. km)
   FIPS code:            20075
   Located within:       Kansas (KS), FIPS 20
   Location:             37.821117 N, 96.858281 W
   ZIP Codes (1990):     67042
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    El Dorado, KS
    El Dorado