Adams County, Colorado

County seat: Brighton · Population 554,668 (2025) · 1,167 sq mi

Adams County is the 5th most populous of Colorado's 64 counties, with 554,668 people (2025 estimate). Its county seat is Brighton. It is part of the Region 3: Denver Metropolitan Area region, one of the 14 Planning and Management Regions of Colorado. The map shows its 10 cities and towns and the 7 neighboring counties.

Map of Adams County, Colorado with cities, towns and the county boundary
Adams County, Colorado with its cities and towns, unincorporated communities (CDPs) and neighboring counties. Boundaries: U.S. Census Bureau, 2025. Free to use with attribution (CC BY 4.0).
Download PDF (Letter) 123 KBPNG image 80 KBColorado county map

Adams County facts

County seat
Brighton
Population (2025 estimate)
554,668 +6.8% since 2020
Land area
1,167 sq mi 39th largest of 64
Water area
17 sq mi
Population density
475 per sq mi
Established
1902
Same name
One of 12 Adams Counties in the US
Named after
Alva Adams American politician (1850-1922)
Largest city
Thornton 147,766 in the county
Median household income
$94,571
Cities and towns
10 plus 10 CDPs
ZIP codes
35
Time zone
Mountain
FIPS code
08001

Cities and towns in Adams County

Adams County has 10 incorporated cities, towns and villages. Populations count the people living inside Adams County; cities that cross a county line also list the other counties.

NameTypePopulation 2025Also in
ThorntonCity147,766Weld County
Commerce CityCity72,345
WestminsterCity70,485Jefferson County
AuroraCity61,110Arapahoe and Douglas counties
Brighton (county seat)City44,934Weld County
NorthglennCity38,869Weld County
Federal HeightsCity14,075
BennettTown3,777Arapahoe County
ArvadaCity2,793Jefferson County
LochbuieTown0Weld County

Unincorporated communities (CDPs)

Census-designated places are communities without their own city government; the county provides their services.

CommunityPopulationAlso in
Sherrelwood18,692
Welby16,197
Berkley10,789
Derby8,453
Twin Lakes8,030
Shaw Heights5,565
Todd Creek5,379
Strasburg2,171Arapahoe County
North Washington294
Watkins63Arapahoe County

ZIP codes in Adams County

35 ZIP codes reach into Adams County. ZIP codes ignore county lines, so some also cover a neighboring county.

Population of Adams County, 2020–2025

Adams County grew by 35,088 people (+6.8%) between April 2020 and July 2025: 14,545 more births than deaths and a net gain of 20,049 people from migration.

Year (July 1)Population
2020520,411
2021523,159
2022528,035
2023537,158
2024549,257
2025554,668

Neighboring counties

Printable Adams County map

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Sources

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