When was Adams County founded?

Adams County was founded in 1902, formed from Arapahoe County and Xx County, and named after Alva Adams.

What is the county seat of Adams County?

The county seat of Adams County is Brighton.

Is there an online parcel map for Adams County?

Yes. A public source publishes a parcel map of 188,785 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Adams County's boundary or name changed?

Adams County was created in 1902 from Arapahoe County and Xx County. Since then the Atlas of Historical County Boundaries records 27 later changes, chiefly involving Denver County, Broomfield County and C.b. County.

Is my lot in a flood zone?

We do not have flood maps for Adams County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

County · code 08001

Adams CountyColorado

Adams County, Colorado is a county in the Denver metropolitan area with its seat in Brighton. The county was created from Arapahoe County in 1902 and named after Alva Adams.

Founded1902
County seatBrighton
Named forAlva Adams
Land area1,167 sq mi + 17 sq mi water
Population519,572 2020 Census
Parcels mapped188,785 checked 15 October 2026

Open the free map Click any parcel in Adams County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1902 from Arapahoe County and Xx County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Adams County was created from Arapahoe County, with an act passed on 15 April 1901 that took effect on 15 November 1902 following adoption of article XX of the Colorado Constitution in the November 1902 election. Within months of its formation, Adams County lost territory to Washington and Yuma counties in 1903. Beginning in 1941, Adams County gradually lost land to Denver through multiple annexations, including airport additions and industrial areas between 1941 and 1963.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

1902
Adams County created Adams created from Arapahoe. Act passed 15 April 1901; took effect 15 November 1902 following adoption of article Xx of the Colorado Constitution in the November 1902 election.
from Arapahoefrom Xx
15 November 1902 · Colo. Laws 1901, 13th sess., ch. 57, pp. 133-137
1903
Lost territory Adams lost to Washington and Yuma.
to Washington to Yuma
12 May 1903 · Colo. Laws 1903, 14th sess., chs. 81-82, pp. 169-176; Colo. Laws 1901, 13th sess., ch. 57, sec. 14/p. 137
1941
Lost territory Adams lost to Denver; 1st Airport Addition, 26th Avenue & Yosemite St.
to Denver
11 December 1941 · City & County Map; Annexation Map
1942
Lost territory Adams lost to Denver; 2nd Airport Addition, 32nd Ave. & Havana St.
to Denver
30 November 1942 · City & County Map; Annexation Map
1949
Lost territory Adams lost to Denver; Jett & Stillman, 52nd Ave. & Platte River.
to Denver
9 April 1949 · Annexation Map

Show all 28 changes (23 more)

1902
Adams County created Adams created from Arapahoe. Act passed 15 April 1901; took effect 15 November 1902 following adoption of article Xx of the Colorado Constitution in the November 1902 election.
from Arapahoefrom Xx
15 November 1902 · Colo. Laws 1901, 13th sess., ch. 57, pp. 133-137
1903
Lost territory Adams lost to Washington and Yuma.
to Washington to Yuma
12 May 1903 · Colo. Laws 1903, 14th sess., chs. 81-82, pp. 169-176; Colo. Laws 1901, 13th sess., ch. 57, sec. 14/p. 137
1941
Lost territory Adams lost to Denver; 1st Airport Addition, 26th Avenue & Yosemite St.
to Denver
11 December 1941 · City & County Map; Annexation Map
1942
Lost territory Adams lost to Denver; 2nd Airport Addition, 32nd Ave. & Havana St.
to Denver
30 November 1942 · City & County Map; Annexation Map
1949
Lost territory Adams lost to Denver; Jett & Stillman, 52nd Ave. & Platte River.
to Denver
9 April 1949 · Annexation Map
1950
Lost territory Adams lost to Denver; C.B. & Q. Industrial, Colorado Blvd. & 52nd St.
to Denverto C.b.
16 February 1950 · Annexation Map
1951
Lost territory Adams lost to Denver; 3rd Airport Addition, Havana St. & 26th Ave.
to Denver
29 October 1951 · Annexation Map
1953
Lost territory Adams lost to Denver; 4th Airport Addition, Yosemite St. & Montview Blvd.
to Denver
2 April 1953 · Annexation Map
1953
Lost territory Adams lost to Denver; 5th Airport Addition, Lima St. & 26th Ave.
to Denver
2 October 1953 · Annexation Map
1960
Lost territory Adams lost to Denver; Airport Annexation.
to Denver
28 December 1960 · Annexation Map
1961
Lost territory Adams lost to Denver; Union Pacific, Smith Rd. & Havana St.
to Denver
3 July 1961 · Annexation Map
1963
Lost territory Adams lost to Denver; Marycrest, Federal Blvd. & W. 52nd Ave.
to Denver
6 June 1963 · Annexation Map
1964
Lost territory Adams lost to Denver; Stapleton East, Havana St. & E. 56th Ave.
to Denver
11 February 1964 · Annexation Map
1964
Lost territory Adams lost to Denver; Stapleton West, 56th Ave. & Quebec St.
to Denver
30 November 1964 · Annexation Map
1964
Lost territory Adams lost small area to Denver; Associated Grocers, Valley Hwy. & 52nd Ave.
to Denver
31 December 1964 · Annexation Map
1965
Lost territory Adams lost to Denver; Interstate, Havana St. & Interstate Hwy. 70.
to Denver
13 September 1965 · Annexation Map
1965
Lost territory Adams lost small area to Denver; Union Pacific #2, Smith Road & Peoria St.
to Denver
13 December 1965 · Annexation Map
1966
Lost territory Adams lost to Denver; Treatment Plant, Clifford Ave. between Lafayette St. & Downing St.
to Denver
28 March 1966 · Annexation Map
1966
Lost territory Adams lost to Denver: Treatment Plant #2, Clifford Ave. (54th Ave.) between Downing St. & Ogden St.
to Denver
18 April 1966 · Annexation Map
1968
Lost territory Adams lost small area to Denver; Marycrest #2, W. 54th & Columbine Road.
to Denver
13 May 1968 · Annexation Map
1970
Lost territory Adams lost to Denver; Stapleton North, 56th Ave. & Yosemite St.
to Denver
6 January 1970 · Annexation Map
1970
Lost territory Adams lost to Denver; Franklin-54th, Franklin St. & 54th Ave.
to Denver
28 September 1970 · Annexation Map
1971
Lost territory Adams lost to Denver; North Franklin, 54th Ave. & Franklin St.
to Denver
11 November 1971 · Annexation Map
1972
Lost territory Adams lost to Denver; Pump Station-56th Ave., 56th Ave. & Roslyn St.
to Denver
6 June 1972 · Annexation Map
c. 1973
Lost territory Adams lost small area to Denver; W. 52nd Ave. & Lincoln St.
to Denver
31 December 1973 · Annexation Map
c. 1979
Lost territory Adams lost to Denver.
to Denver
31 December 1979 · USGS, 7.5 Minute Series, Sable Quadrangle, edition of 1965 [photorevised 1971] and edition of 1965 [photorevised 1979]
1988
Lost territory Adams lost to Denver; Denver International Airport annexation. Referendum held 17 May 1988.
to Denver
17 May 1988 · Dempsey, 142
2001
Lost territory Adams lost to creation of Broomfield.
to Broomfield
15 November 2001 · Colo. Laws 2001, 63d sess., ch. 103, pp. 256-274

Land and parcels

What the maps cover in Adams

Who publishes each layer, how good it is, and when we last checked.

Parcels Good enough

Lot lines and tax-map numbers for 188,785 parcels. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 11 October 2026 · checked 15 October 2026
Address points Missing

No public address points layer found for Adams County yet.
Buildings Reference

Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026

Official: from the office that keeps the record
Good enough: a reliable statewide or national copy
Fallback: a guide only; check the official record
Missing: nothing public found yet

People and land

Adams by the Census

Population

519,572 2020 Census count

Housing units

186,544 2020 Census count

Land area

1,167 square miles

Water area

17 square miles

People per sq mi

445 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Adams County's official site

We have found the county's site but not its offices yet; start there.

County government

County government
The official website of Adams County.
co.adams.co.us

See your own lot on these maps

Open Adams County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

Open the free map no sign-in Pro early access

Questions

Common questions about Adams County

When was Adams County founded?: Adams County was founded in 1902, formed from Arapahoe County and Xx County, and named after Alva Adams.
What is the county seat of Adams County?: The county seat of Adams County is Brighton.
Is there an online parcel map for Adams County?: Yes. A public source publishes a parcel map of 188,785 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Adams County's boundary or name changed?: Adams County was created in 1902 from Arapahoe County and Xx County. Since then the Atlas of Historical County Boundaries records 27 later changes, chiefly involving Denver County, Broomfield County and C.b. County.
Is my lot in a flood zone?: We do not have flood maps for Adams County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby