Jefferson County, Colorado Information (Geography)
Jefferson County Courthouse in Golden
Gateway to the Rocky Mountains
Location within the U.S. state of Colorado
Colorado's location within the U.S.
|Founded||November 1, 1861|
|Named for||Thomas Jefferson|
|• Total||774 sq mi (2,000 km2)|
|• Land||764 sq mi (1,980 km2)|
|• Water||9.8 sq mi (25 km2) 1.3%%|
| • Estimate |
|• Density||752/sq mi (290/km2)|
|Time zone||UTC−7 ( Mountain)|
|• Summer ( DST)||UTC−6 ( MDT)|
|Congressional districts||1st, 2nd, 7th|
Jefferson County, is one of the 64 counties in the U.S. state of Colorado. As of the 2010 census, the population was 534,543,  making it the fourth-most populous county in Colorado. The county seat is Golden,  and the most populous city is Lakewood.
Jefferson County is included in the Denver- Aurora-Lakewood, CO Metropolitan Statistical Area. Located along the Front Range of the Rocky Mountains, Jefferson County is adjacent to the state capital of Denver.
In 2010, the center of population of Colorado was located in Jefferson County. 
The county's slogan is the "Gateway to the Rocky Mountains", and it is commonly nicknamed Jeffco. The name Jeffco is incorporated in the name of the Jeffco School District, the Jeffco Business Center Metropolitan District No. 1, and several businesses located in Jefferson County. Jeffco is also incorporated in the unofficial monikers of many Jefferson County agencies. The Rocky Mountain Metropolitan Airport operated by Jefferson County was previously known as the Jeffco Airport.
A major employer in Jefferson County is the large Coors Brewing Company in Golden. Also, the state-supported Colorado School of Mines is located in Jefferson County, offering programs in STEM topics such as mining, geology, chemistry, and engineering.
- 1 History
- 2 Geography
- 3 Demographics
- 4 Education
- 5 Government and infrastructure
- 6 Recreation
- 7 Communities
- 8 See also
- 9 References
- 10 External links
On August 25, 1855, the Kansas Territorial Legislature created Arapahoe County to govern the entire western portion of the territory. The county was named for the Arapaho Nation of Native Americans that lived in the region.
In June 22, 1850, gold was discovered along the South Platte River in Arapahoe County (in present-day Englewood). This discovery precipitated the Pike's Peak Gold Rush. Many residents of the mining region felt disconnected from the remote territorial governments of Kansas and Nebraska, so they voted to form their own Territory of Jefferson on October 24, 1859. The following month, the Jefferson Territorial Legislature organized 12 counties for the new territory, including Jefferson County. Jefferson County was named for the namesake of the Jefferson Territory, Thomas Jefferson, the principal author of the Declaration of Independence and the nation's third president.  Golden City served as the county seat of Jefferson County. Robert Williamson Steele, Governor of the Provisional Government of the Territory of Jefferson from 1859 to 1861, built his home in the county at Mount Vernon and later at Apex.
The Jefferson Territory never received federal sanction, but during his last week in office, President James Buchanan signed an act which organized the Territory of Colorado on February 28, 1861.  That November 1, the new Colorado General Assembly organized the 17 original counties of Colorado, including a new Jefferson County. In 1908, the southern tip of Jefferson County was transferred to Park County, reducing Jefferson County to its present length of 54 miles (87 km). Several annexations by the City & County of Denver and the 2001 consolidation of the City & County of Broomfield removed the east and extreme northwestern portion of the county, respectively.
Jefferson County is one of the few counties in the United States to border as many as ten counties.
- Alderfer/Three Sisters Park
- Apex Park
- Bear Creek Lake Park
- Centennial Cone Park
- Clear Creek Canyon Park
- Coal Creek Canyon
- Crown Hill Park
- Deer Creek Canyon Park
- Elk Meadow Park
- Evergreen Lake
- Fairmount Trail
- Flying J Ranch Park
- Hildebrand Ranch Park
- Hiwan Homestead Museum
- Lair o' the Bear Park
- Lewis Meadows Park
- Lookout Mountain Nature Center
- Matthews/Winters Park
- Meyer Ranch Park
- Mount Falcon Park
- Mount Galbraith Park
- Mount Glennon
- Mount Lindo
- North Table Mountain Park
- Pine Valley Ranch Park
- Ranson/Edwards Homestead Ranch
- Reynolds Park
- Sister City Park
- South Table Mountain Park
- South Valley Park
- Standley Lake Regional Park
- Van Bibber Park
- Welchester Tree Grant Park
- White Ranch Park
- Windy Saddle Park
- Urban Trails
|U.S. Decennial Census
1790-1960  1900-1990 
1990-2000  2010-2015 
As of the census  of 2000, there were 527,056 people, 206,067 households, and 140,537 families residing in the county. The population density was 683 people per square mile (264/km²). There were 212,488 housing units at an average density of 275 per square mile (106/km²). The racial makeup of the county was 90.59% White, 0.89% Black or African American, 0.75% Native American, 2.28% Asian, 0.08% Pacific Islander, 3.23% from other races, and 2.18% from two or more races. 9.95% of the population were Hispanic or Latino of any race.
There were 206,067 households out of which 33.40% had children under the age of 18 living with them, 55.10% were married couples living together, 9.10% had a female householder with no husband present, and 31.80% were non-families. 24.50% of all households were made up of individuals and 6.30% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.03.
In the county, the population was spread out with 25.30% under the age of 18, 8.10% from 18 to 24, 32.10% from 25 to 44, 24.90% from 45 to 64, and 9.60% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 99.00 males. For every 100 females age 18 and over, there were 96.80 males.
The median income for a household in the county was $57,339, and the median income for a family was $67,310. Males had a median income of $45,306 versus $32,372 for females. The per capita income for the county was $28,066. About 3.40% of families and 5.20% of the population were below the poverty line, including 5.80% of those under age 18 and 5.10% of those age 65 or over.
- The Federal Correctional Institution, Englewood is in unincorporated Jefferson County. 
- The Rocky Flats Plant produced nuclear weapons in Jefferson County from 1952 until 1989.
- The Jefferson County Public Library, established in 1952.
- The Jefferson County Government Center, also known as the "Taj Mahal".
- American Discovery Trail
- Apex National Recreation Trail
- Big Dry Creek National Recreation Trail
- Colorado Trail
- Platte River Greenway National Recreation Trail
- Two Ponds National Recreation Trail
- Applewood Golf Course
- Bear Creek Golf Club
- Evergreen Golf Course
- Foothills Golf Course
- Fossil Trace Golf Course
- Fox Hollow Golf Course
- Heritage Golf Course at Westmoor
- Hiwan Golf Club
- Homestead Golf Course
- Indian Tree Golf Club
- Lake Arbor Golf Course
- Lakewood Country Club
- Racoon Creek Golf Course
- Rolling Hills Country Club
- Arapahoe County, Kansas Territory
- Colorado metropolitan areas
- Denver-Aurora, CO Combined Statistical Area
- Denver-Aurora-Lakewood, CO Metropolitan Statistical Area
- Front Range Urban Corridor
- Index of Colorado-related articles
- Jefferson County, Colorado Territory
- Jefferson County, Jefferson Territory
- National Register of Historic Places listings in Jefferson County, Colorado
- North Central Colorado Urban Area
- Outline of Colorado
- Pike's Peak Gold Rush
- "State & County QuickFacts". United States Census Bureau. Archived from the original on June 6, 2011. Retrieved June 8, 2014.
- "Find a County". National Association of Counties. Archived from the original on 2011-05-31. Retrieved 2011-06-07.
- "Centers of Population by State: 2010". United States Census Bureau. Archived from the original on January 3, 2014. Retrieved June 8, 2014.
- Gannett, Henry (1905). The Origin of Certain Place Names in the United States. Govt. Print. Off. p. 168.
- "An Act to provide a temporary Government for the Territory of Colorado" ( PDF). Thirty-sixth United States Congress. 1861-02-28. Retrieved 2007-11-26.
- "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 April 26, 2015. Retrieved June 8, 2014.
- "Historical Census Browser". University of Virginia Library. Retrieved June 8, 2014.
- "Population of Counties by Decennial Census: 1900 to 1990". United States Census Bureau. Retrieved June 8, 2014.
- "Census 2000 PHC-T-4. Ranking Tables for Counties: 1990 and 2000" (PDF). United States Census Bureau. Retrieved June 8, 2014.
- "American FactFinder". United States Census Bureau. Retrieved 2011-05-14.
- Dwyer-Lindgren, Laura (8 May 2017). "Inequalities in Life Expectancy Among US Counties, 1980 to 2014". JAMA Internal Medicine. 177: 1003–1011. doi: 10.1001/jamainternmed.2017.0918. PMC 5543324. PMID 28492829. Retrieved 9 May 2017.
- " FCI Englewood Contact Information." Federal Bureau of Prisons. Retrieved on July 28, 2010.
- Leip, David. "Dave Leip's Atlas of U.S. Presidential Elections". uselectionatlas.org. Retrieved May 26, 2017.
|Wikimedia Commons has media related to Jefferson County, Colorado.|
- Jefferson County Government website
- Colorado County Evolution by Don Stanwyck
- Colorado Historical Society
- Jefferson County Open Space Parks