|Boulder County, Colorado|
Boulder County Courthouse
Location in the U.S. state of Colorado
Colorado's location in the U.S.
|Founded||November 1, 1861|
|Named for||large granite boulders in area|
|• Total||740 sq mi (1,917 km2)|
|• Land||726 sq mi (1,880 km2)|
|• Water||14 sq mi (36 km2), 1.9%|
|• ( 2017)||322,514 |
|• Density||450/sq mi (172/km2)|
|Congressional districts||2nd, 4th|
|Time zone||Mountain: UTC−7/ −6|
Boulder County is one of the 64 counties of the U.S. state of Colorado of the United States. As of the 2010 census, the population was 294,567.  The most populous municipality in the county and the county seat is Boulder. 
- 1 History
- 2 Geography
- 3 Demographics
- 4 Government
- 5 Politics
- 6 Local courts
- 7 Communities
- 8 See also
- 9 References
- 10 External links
Boulder County was one of the original 17 counties created by the Territory of Colorado on November 1, 1861. The county was named for Boulder City and Boulder Creek, so named because of the abundance of boulders in the area. Boulder County retains essentially the same borders as in 1861, although a 27.5 square miles (71.2 km2) of its southeastern corner and its approximate population of 40,000 became part of the City and County of Broomfield in 2001.
- Larimer County, Colorado – north
- Weld County, Colorado – east
- City and County of Broomfield, Colorado – southeast
- Jefferson County, Colorado – south
- Gilpin County, Colorado – south
- Grand County, Colorado – west
|U.S. Decennial Census
1790-1960  1900-1990 
1990-2000  2010-2015 
As of the census  of 2000, there were 271,651 people, 114,680 households, and 68,808 families residing in the county. The population density was 392 people per square mile (151/km²). There were 119,900 housing units at an average density of 162 per square mile (62/km²). The racial makeup of the county was 88.54% White, 0.88% Black or African American, 0.61% Native American, 3.06% Asian, 0.06% Pacific Islander, 4.67% from other races, and 2.18% from two or more races. 10.46% of the population were Hispanic or Latino of any race.
There were 114,680 households out of which 30.70% had children under the age of 18 living with them, 48.90% were married couples living together, 7.70% had a female householder with no husband present, and 40.00% were non-families. 26.30% of all households were made up of individuals and 5.50% had someone living alone who was 65 years of age or older. The average household size was 2.47 and the average family size was 3.03.
In the county, the population was spread out with 22.90% under the age of 18, 13.40% from 18 to 24, 33.60% from 25 to 44, 22.30% from 45 to 64, and 7.80% who were 65 years of age or older. The median age was 33 years. For every 100 females, there were 102.20 males. For every 100 females age 18 and over, there were 101.70 males.
In 2014, the median income for a household in the county was $69,407, and the median income for a family was $94,938.  Males had a median income of $65,489 versus $48,140 for females. About 7.0% of families and 14.6% of the population were below the poverty line, including 14.6% of those under age 18 and 5.9% of those age 65 or over.
In 2017 Bloomberg ranked the Boulder metropolitan area as the top "brain" area in the US. 
Boulder County is divided into three districts each represented by a commissioner elected county-wide. The three commissioners comprise the county Board of Commissioners and represent the county as a whole. Each commissioner must reside in their respective district and may be elected to a maximum of two four-year terms.
The Board of County Commissioners are full-time public servants and approve the budget for the entire County government. The Board also oversees the management of 10 County departments and the daily operations of the county, work that is done by a county manager or a chief administrative officer in some counties.
Boulder County has seven other county-wide elected officials, including the District Attorney, who represents the 20th Judicial District. 
|Name||Office||Year Term Began||Year Re-Elected|
|Deb Gardner||County Commissioner||2012 [a]||2016|
|Elise Jones||County Commissioner||2012||2016|
|Cindy Domenico||County Commissioner||2007 [b]||2010|
|Jerry Roberts||Assessor||2007 [c]||2010|
|Hillary Hall [d]||Clerk and Recorder||2006||2010|
|Emma R. Hall [d]||Coroner||2010||2014|
|Stanley L. Garnett||District Attorney||2008||2012|
|Joe Pelle||Sheriff||2002||2006, 2010, 2014|
- Deb Gardner of Longmont was appointed to the Boulder County Board of Commissioners by a majority vote of a Boulder County Democratic Party vacancy committee on January 8, 2012, and was sworn into office on January 10 replacing Ben Pearlman who resigned as commissioner on January 1, 2012 after being selected to head the County Attorney’s office.
- Incumbent Ton Mayer died, and Cindy Domenico was appointed in July 2007 to fill the vacant seat. In 2008, voters elected Domenico to complete the remainder of the term that continued through 2010.
- Incumbent Cindy Domenico resigned after being elected to the post of Boulder County Commissioner. Jerry Roberts was appointed to fill the vacant seat in July 2007. In 2008, voters elected Roberts to complete the remainder of the term that continued through 2010.
- Hillary Hall and Emma Hall are not related.
In 2000, Green Party presidential candidate Ralph Nader took 11.82% of the vote in Boulder County, more than twice the 5.25% he took statewide in Colorado, and more than four times his 2.73% nationwide vote share. 
Boulder County has also demonstrated its liberal leanings in referenda on social issues, such as in 2006, when nearly 2/3 of Boulder County voters voted to reject Amendment 43, a constitutional amendment defining marriage as between one man and one woman. Although the amendment passed statewide with 55% of the vote, only 33% of Boulder County supported it.  In 2012, over 66% of Boulder County voted in favor of Amendment 64, legalizing marijuana in the state of Colorado.
The 20th Judicial District of Colorado, the state trial court of general jurisdiction, serves and is coextensive with Boulder County. As of 2009 the 20th Judicial Circuit has eight District Court judges. The Boulder County Court, the state trial court of limited jurisdiction, consists of five judges and six magistrates.
Boulder County has two combined courthouses:
- The Boulder County Justice Center is located in the City of Boulder and is headquarters to the 20th Judicial District of Colorado. The office of the district attorney is also here, as is the Juvenile Assessment Center, the county's combined assessment and detention facility.
- The Longmont Courthouse in the City of Longmont acts as an extension of the County Court and the District Attorney's Office. 
- Erie (partly in Weld County)
- Superior (partly in Jefferson County)
- Town of Ward
- Bark Ranch
- Bonanza Mountain Estates
- Coal Creek (partly in Gilpin County and Jefferson County)
- Eldorado Springs
- Gold Hill
- Hidden Lake
- Lazy Acres
- Mountain Meadows
- Paragon Estates
- Pine Brook Hill
- Seven Hills
- St. Ann Highlands
- Tall Timber
- Jackson County, Jefferson Territory
- Colorado census statistical areas
- National Register of Historic Places listings in Boulder County, Colorado
- Front Range Urban Corridor
- North Central Colorado Urban Area
- 2013 Colorado floods
- "Population and Housing Unit Estimates". U.S. Census Bureau. August 15, 2017. Retrieved August 15, 2017.
- "State & County QuickFacts". United States Census Bureau. Retrieved June 7, 2014.
- "Find a County". National Association of Counties. Archived from the original on May 31, 2011. Retrieved 2011-06-07.
- "OMB Bulletin No. 10-02: Update of Statistical Area Definitions and Guidance on Their Uses" (PDF). United States Office of Management and Budget. December 1, 2009. Archived from the original (PDF) on March 16, 2012. Retrieved April 19, 2012.
- "US Gazetteer files: 2010, 2000, and 1990". United States Census Bureau. 2011-02-12. Retrieved 2011-04-23.
- "American FactFinder". Retrieved March 23, 2018.
- "U.S. Decennial Census". United States Census Bureau. Archived from the original on May 12, 2015. Retrieved June 7, 2014.
- "Historical Census Browser". University of Virginia Library. Retrieved June 7, 2014.
- "Population of Counties by Decennial Census: 1900 to 1990". United States Census Bureau. Retrieved June 7, 2014.
- "Census 2000 PHC-T-4. Ranking Tables for Counties: 1990 and 2000" (PDF). United States Census Bureau. Retrieved June 7, 2014.
- "American FactFinder". United States Census Bureau. Archived from the original on September 11, 2013. Retrieved 2011-05-14.
- "American Fact Finder: Boulder County, Colorado". United States Census Bureau. Retrieved 23 March 2016.
- Vincent Del Giudice, Wei Lu, and Agnel Philip (10 October 2017). "The Smartest Americans Are Heading West". Retrieved 11 October 2017 – via www.bloomberg.com.
- "Boulder County Board of County Commissioners". Boulder County. Archived from the original on December 10, 2007. Retrieved December 1, 2009.
- "Dave Leip's Atlas of U.S. Presidential Elections". Retrieved January 5, 2013.
- Leip, David. "Dave Leip's Atlas of U.S. Presidential Elections". uselectionatlas.org. Retrieved May 26, 2017.
- "Dave Leip's Atlas of U.S. Presidential Elections". Retrieved January 5, 2013.
- "20th Judicial District/Boulder County". Colorado State Courts. Archived from the original on January 27, 2010. Retrieved December 1, 2009.
- Boulder County Government website
- Boulder County USGenWeb
- Colorado County Evolution by Don Stanwyck
- Colorado Historical Society
- Rocky Mountain National Park website