Boulder County, Colorado

Boulder County
Boulder County Courthouse
Location within the U.S. state of Colorado
Colorado's location within the U.S.
Coordinates: 40°05′N 105°22′W / 40.09°N 105.36°W / 40.09; -105.36
Country United States
State Colorado
FoundedNovember 1, 1861
Named afterlarge granite boulders in area
SeatBoulder
Largest cityBoulder
Area
  Total
740 sq mi (1,900 km2)
  Land726 sq mi (1,880 km2)
  Water14 sq mi (40 km2)  1.9%
Population
 (2020)
  Total
330,758
  Estimate 
(2024)
330,262
  Density450/sq mi (170/km2)
Time zoneUTC−7 (Mountain)
  Summer (DST)UTC−6 (MDT)
Congressional districts2nd, 4th
Websitewww.bouldercounty.org

Boulder County is a county located in the U.S. state of Colorado of the United States. As of the 2020 census, the population was 330,758. The most populous municipality in the county and the county seat is Boulder. Boulder County comprises the Boulder, Colorado Metropolitan Statistical Area, which is included in the DenverAurora, Colorado Combined Statistical Area.