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Arapahoe County, Colorado facts for kids

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Arapahoe County
Little Dry Creek in Englewood
Little Dry Creek in Englewood
Map of Colorado highlighting Arapahoe County
Location within the U.S. state of Colorado
Map of the United States highlighting Colorado
Colorado's location within the U.S.
Country  United States
State  Colorado
Founded November 1, 1861
Named for The Arapaho Nation
Seat Littleton
Largest city Aurora
 • Total 805 sq mi (2,080 km2)
 • Land 798 sq mi (2,070 km2)
 • Water 7.3 sq mi (19 km2)  0.9%%
 • Total 655,070
 • Density 821/sq mi (317/km2)
Time zone UTC−7 (Mountain)
 • Summer (DST) UTC−6 (MDT)
Congressional districts 1st, 4th, 6th
Third most populous Colorado county

Arapahoe County ( 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.


On August 25, 1855, the Kansas Territorial Legislature created a huge Arapahoe County to govern the entire western portion of the Territory of Kansas. The county was named for the Arapaho Nation who lived in the region.

In July 1858, 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 a smaller Arrappahoe County. Denver City served as the county seat of Arapahoe County.

The Jefferson Territory never received federal sanction, and when the State of Kansas was admitted to the Union on January 29, 1861, the mining regions temporarily reverted to unorganized territory. On February 28, 1861, Congress passed an act organizing the Territory of Colorado, using present-day borders. On November 1, 1861, the Colorado Territorial Assembly organized the 17 original counties of Colorado, including a new Arapahoe County. Arapahoe County originally stretched from the line of present-day Sheridan Boulevard 160 miles (258 kilometers) east to the Kansas border, and from the line of present-day County Line Road 30 miles (48 kilometers) north to the Parallel 40° North (168th Avenue). Denver City served as the county seat of Arapahoe County until 1902.

In 1901, the Colorado General Assembly voted to split Arapahoe County into three parts: a new consolidated City and County of Denver, a new Adams County, and the remainder of the Arapahoe County to be renamed South Arapahoe County. A ruling by the Colorado Supreme Court, subsequent legislation, and a referendum delayed the reorganization until November 15, 1902. Governor James Bradley Orman designated Littleton as the temporary county seat of South Arapahoe County. On April 11, 1903, the Colorado General Assembly changed the name of South Arapahoe County back to Arapahoe County. On November 8, 1904, Arapahoe County voters chose Littleton over Englewood by a vote of 1310 to 829 to be the permanent county seat.


Arapahoe County Justice Center
The contemporary Arapahoe County Courthouse in Dove Valley.

According to the U.S. Census Bureau, the county has a total area of 805 square miles (2,080 km2), of which 798 square miles (2,070 km2) is land and 7.3 square miles (19 km2) (0.9%) is water. The county measures 72 miles (116 kilometers) east to west and 4 to 12 miles (6 to 19 kilometers) south to north.

Two exclaves of Arapahoe County are entirely surrounded by the City and County of Denver, the City of Glendale and the Holly Hills neighborhood, a census-designated place.

Adjacent counties

Major highways

  • Interstate 25
  • Interstate 70
  • Interstate 225
  • E-470 (tollway)

State park

Historic trails

  • Smoky Hill Trail
  • South Platte Trail

Recreation trails


Historical population
Census Pop.
1870 6,829
1880 38,644 465.9%
1890 132,135 241.9%
1900 153,017 15.8%
1910 10,263 −93.3%
1920 13,766 34.1%
1930 22,647 64.5%
1940 32,150 42.0%
1950 52,125 62.1%
1960 113,426 117.6%
1970 162,142 42.9%
1980 293,621 81.1%
1990 391,511 33.3%
2000 487,967 24.6%
2010 572,003 17.2%
2020 655,070 14.5%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2020

As of the census of 2000, 487,967 people, 190,909 households, and 125,809 families were residing in the county. The population density was 608 people/sq mi (235/km2). The 196,835 housing units averaged 245/sq mi (95/km2). The racial makeup of the county was 79.93% White, 7.67% African American, 0.66% Native American, 3.95% Asian, 0.12% Pacific Islander, 4.51% from other races, and 3.16% from two or more races. Hispanics or Latinos of any race made up 11.81% of the population .

Of the 190,909 households, 34.90% had children under the age of 18 living with them, 51.20% were married couples living together, 10.60% had a female householder with no husband present, and 34.10% were not families. About 27.00% of all households were made up of individuals, and 5.90% had someone living alone who was 65 years of age or older. The average household size was 2.53, and the average family size was 3.11.

In the county, the age distribution was 26.70% under 18, 8.60% from 18 to 24, 33.10% from 25 to 44, 23.00% from 45 to 64, and 8.60% who were 65 or older. The median age was 34 years. For every 100 females, there were 97.10 males. For every 100 females age 18 and over, there were 94.20 males.

The median income for a household was $53,570, and for a family was $63,875. Males had a median income of $41,601 versus $31,612 for females. The per capita income for the county was $28,147. About 4.20% of families and 5.80% of the population were below the poverty line, including 7.00% of those under age 18 and 5.10% of those age 65 or over.




Census-designated places

Unincorporated communities

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