Boulder County, Colorado

Boulder County: County in Colorado, United States


Boulder County is a county located in the U.S. state of Colorado. As of the 2010 census, the population was 294,567 and a population density of 151 people per km². After 10 years in 2020 county had an estimated population of 327,171 inhabitants. Its county seat is Boulder. The county was created 161 years ago in 1861.

Quick Facts about Boulder County

Population : 327,171 (2020)
Country : United States of America
State : Colorado (United States)
Twitter username : bouldercounty
Area : 1946 km2
Water as percent of area : 1.9%
Land as percent of area : 98.1%
Named for : Boulder Creek, Boulder
Altitude : 7,090 feet / 2161 meters
Capital : Boulder
Establishment : November 11, 1861
Time Zone : America/Denver
Local time : 22:40:13 (3rd June 2023)
Density : 168 Pop. per km² as of 2020
Population growth : 9.97% (2010-2020)
Boulder County locator map
Location of Boulder County on Colorado map.
Boulder County Courthouse '31861249120' image
Boulder County Courthouse '31861249120'
Boulder County Courthouse '31861249120' image


Boulder County is located at 40°5'33"N 105°21'28"W (40.0924600, -105.3577000). It has 5 neighbors: Broomfield County, Gilpin County, Jefferson County, Larimer County and Weld County.

Boulder County map

The largest city of Boulder County is Boulder with a population of 107,645. Other cities include, Longmont population 98,445, Lafayette population 28,579 and Louisville population 19,060. See all Boulder County cities & populated places.

Boulder County Populated Places

Cities, Towns, Neighborhoods & Other Populated Places in Boulder County.

City Name Population Title
Boulder 107,645 City in Colorado, United States of America
Longmont 98,445 City in Colorado, USA
Erie 30,318 Town in Boulder County, Colorado, USA
Lafayette 28,579 City in Colorado
Louisville 19,060 City in Colorado
Superior 13,413 Statutory Town in Boulder and Jefferson counties in the U.
Niwot 4,006 Census designated place
Lyons 2,058 Town in Boulder County, Colorado, United States
Nederland 1,557 Town in Colorado, United States
Coal Creek 350 Town in Fremont County, Colorado, United States
Jamestown 254 Town in Colorado, USA
Ward 168 Town in Colorado, United States

Boulder County has 5 neighbours.


The population of Boulder County increased by 9.97% in 10 years.

Year Population % Change Method
2010 294,567 - census
2011 299,957 1.8% estimation process
2012 304,570 1.51% estimation process
2013 309,323 1.54% estimation process
2014 312,233 0.93% estimation process
2015 318,027 1.82% estimation process
2016 321,250 1% estimation process
2017 322,441 0.37% estimation process
2018 324,636 0.68% estimation process
2019 326,196 0.48% estimation process
2020 327,171 0.3% estimation process

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Colorado Other Counties (more counties)

County Name Population Title
Denver 735,538 Capital city of the state of Colorado, United States; consolidated city and county
Denver County 735,538 County in Colorado, United States, coterminous with the City of Denver
El Paso County 728,310 One of the 64 counties in the U.
Arapahoe County 657,452 County in Colorado, United States
Jefferson County 583,283 County in Colorado, United States
Adams County 519,883 County in Colorado, United States
Colorado Springs 482,131 County seat of El Paso County, Colorado, United States
Aurora 387,377 City in Kane County, Illinois, United States
Douglas County 360,750 County in Colorado, United States
Larimer County 360,428 County in Colorado, United States
Weld County 333,983 County in Colorado, United States
Pueblo County 169,823 County in Colorado, United States
Fort Collins 168,234 Municipality and county seat of Larimer County, Colorado, United States
Lakewood 157,429 City in Colorado
Mesa County 155,603 County in Colorado, United States
Thornton 148,113 City in Adams County, Colorado, United States of America