Arapahoe County, Colorado

Arapahoe County is a county in Colorado, United States, on the southeastern edge of the Denver metropolitan area. It had a population of 655,070 at the 2020 census, making it Colorado’s third most populous county, and covers 798 square miles (2,070 km2) of land centred near 39°39′N 104°40′W.

Littleton is the county seat, and its postal code is 80120. The county holds 8 incorporated cities, 5 incorporated towns and 13 census-designated places, and it sits in the Mountain time zone (UTC−7, UTC−6 during daylight time). Arapahoe County has no civil townships.

Towns & Villages in Arapahoe County

Arapahoe County’s 26 named places split between 8 cities, 5 towns and 13 census-designated places (CDPs) — unincorporated communities the Census Bureau tracks but that have no town government of their own. Several CDPs straddle the county line: Columbine extends into Jefferson County, and Strasburg and Watkins both extend into Adams County.

ZIP Codes

• 80120 — Littleton (county seat)
• 80010–80019, 80040–80047, 80247 — Aurora
• 80112, 80121–80122, 80015–80016 — Centennial
• 80110–80113 — Englewood and Sheridan
• 80111 — Greenwood Village
• 80113 — Cherry Hills Village
• 80246 — Glendale
• 80102 — Bennett and Brick Center
• 80105 — Deer Trail
• 80103 — Byers
• 80136 — Strasburg
• 80137 — Watkins, Comanche Creek and Four Square Mile

Smaller CDPs such as Holly Hills, Peoria, Dove Valley and Columbine share a ZIP with the larger city or unincorporated area that surrounds them rather than carrying one of their own.

Geography

Arapahoe County is 72 miles (116 km) across east to west and only 4 to 12 miles (6 to 19 km) north to south, a long, narrow shape that runs from the eastern edge of metro Denver out into the High Plains. Of its 805 square miles, 798 square miles are land and 7.3 square miles (19 km2) are water. Cherry Creek runs through the county’s western half toward Denver, and Cherry Creek Reservoir, inside Cherry Creek State Park, is the county’s largest body of water.

Arapahoe County borders Denver County to the northwest, Adams County to the north, Washington County to the east, Lincoln County to the southeast, Elbert County to the south, Douglas County to the southwest and Jefferson County to the west.

Demographics

The 2020 census counted 655,070 residents in Arapahoe County. Aurora, with 386,261 people, and Centennial, with 108,418, are by far the two largest communities, together holding roughly three-quarters of the county’s population. Arapahoe County’s median household income runs close to the Colorado median of $92,911, reflecting a mix of working-class Aurora neighborhoods and some of the wealthiest suburbs in the Denver area, including Cherry Hills Village and Greenwood Village. Density across the 798 square miles of land works out to roughly 821 people per square mile, though most residents live on the county’s western quarter — the eastern plains toward Byers and Deer Trail remain sparsely settled farm and ranch country.

Economy & Local Life

Health care and higher education anchor the county’s western cities: the University of Colorado Anschutz Medical Campus in Aurora is one of the largest academic medical centers in the country, and Colorado Technical University runs a Denver South campus in the same area. Buckley Space Force Base, home to the 460th Space Wing, sits on Aurora’s eastern edge and is one of the county’s largest single employers. Centennial and Greenwood Village host a dense cluster of corporate offices along the I-25 Denver Tech Center corridor, while the eastern plains around Byers, Deer Trail and Strasburg stay agricultural, running cattle and dryland wheat.

History

Arapahoe County was organized on November 1, 1861, one of the original 17 counties created when the Colorado Territory was formed, and it took its name from the Arapaho people who lived in the region before white settlement. It once covered a far larger area of the territory, including land later split off to form Denver and several other Front Range counties, which is why local boosters still sometimes call it “Colorado’s First County.” The county predates the Pike’s Peak Gold Rush of 1858–59, and its western towns grew up along the South Platte and Cherry Creek as farming and ranching communities before Denver’s later 20th-century suburban expansion absorbed most of them.

Getting There

Interstates 25 and 225 cross the county’s western cities, and I-70 runs along its northern edge toward the eastern plains; US 85, US 87 and US 285 also pass through.

• Denver — 12 miles northwest of Littleton
• Colorado Springs — 55 miles south of Aurora
• Boulder — 32 miles north of Centennial
• Byers — 35 miles east of Aurora

Denver International Airport, the county’s nearest commercial airport, sits just north of the Arapahoe County line on Aurora’s border.

Frequently Asked Questions

Where is Arapahoe County, Colorado?
It sits on the southeastern edge of metro Denver, running from the city of Denver’s border 72 miles east across the High Plains.

What is the population of Arapahoe County?
655,070 at the 2020 census, Colorado’s third most populous county.

How big is Arapahoe County?
798 square miles (2,070 km2) of land plus 7.3 square miles (19 km2) of water.

What is the county seat of Arapahoe County?
Littleton, postal code 80120.

How many towns and cities are in Arapahoe County?
8 incorporated cities and 5 incorporated towns, plus 13 census-designated places.

What ZIP codes are in Arapahoe County?
ZIP codes run from 80010 in Aurora to 80137 out toward Watkins, with the seat, Littleton, at 80120.

What is Arapahoe County’s largest city?
Aurora, with 386,261 residents at the 2020 census — nearly four times the population of Centennial, the county’s second largest city.

More counties in this state: Towns and villages in Colorado.