Arapahoe County, Colorado

Arapahoe County
Little Dry Creek in Englewood
Location within the U.S. state of Colorado
Colorado's location within the U.S.
Coordinates: 39°38′N 104°20′W / 39.64°N 104.33°W / 39.64; -104.33
Country United States
State Colorado
FoundedNovember 1, 1861
Named afterThe Arapaho Nation
SeatLittleton
Largest cityAurora
Area
  Total
805 sq mi (2,080 km2)
  Land798 sq mi (2,070 km2)
  Water7.3 sq mi (19 km2)  0.9%
Population
 (2020)
  Total
655,070 (3rd)
  Estimate 
(2024)
666,918
  Density820/sq mi (317/km2)
Time zoneUTC−7 (Mountain)
  Summer (DST)UTC−6 (MDT)
Congressional districts1st, 4th, 6th
Websitewww.arapahoegov.com

Arapahoe County (/əˈræpəh/ ə-RAP-ə-hoh) is a county located in the U.S. state of Colorado. As of the 2020 census, its population was 655,070, making it the third-most populous county in Colorado. The county seat is Littleton, and the most populous city is Aurora. The county was named for the Arapaho Native American tribe, who once lived in the region. Arapahoe County is part of the Denver-Aurora-Lakewood metropolitan statistical area. Arapahoe County calls itself "Colorado's First County", since its origins antedate the Pike's Peak Gold Rush.