When was Colusa County founded?

Colusa County was founded in 1850, formed from Butte County, and named after Rancho Colus, California.

What is the county seat of Colusa County?

The county seat of Colusa County is Colusa.

Is there an online parcel map for Colusa County?

Yes. Colusa County publishes a parcel map of 15,056 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Colusa County's boundary or name changed?

Colusa County was created in 1850 from Butte County. Since then the Atlas of Historical County Boundaries records 12 later changes, chiefly involving Tehama County, Butte County and Glenn County.

Who issues building permits in Colusa County?

The county's page on building permits: Building Permits. Inside a city or town, ask that city first.

Who issues septic and well permits in Colusa County?

The county's page on septic systems and wells: Behavioral Health.

Is my lot in a flood zone?

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

County · code 06011

Colusa CountyCalifornia

Colusa County is a California county created in 1850 from Butte County, with its seat in Colusa. The county is named after Rancho Colus.

Founded1850
County seatColusa
Named forRancho Colus, California
Land area1,151 sq mi + 5.6 sq mi water
Population21,839 2020 Census
Parcels mapped15,056 checked 15 October 2026

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

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1850 from Butte County

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

Colusa County was formed in 1850 from Butte County, and named after Rancho Colus, California. Colusa is the county seat.

Deeds and plats from before 1850 for land now in Colusa County may have been recorded in Butte County.

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

1850
Colusa County created Colusi (now Colusa) created from non-county area; Colusi not fully organized, attached to Butte "for judicial purposes."
from Butte
18 February 1850 · Calif. Stats. 1849, 1st sess., ch. 15, sec. 22/p. 62
1851
Gained territory Colusi (now Colusa) gained from Yolo, lost to Shasta.
from Yolo from Shasta
25 April 1851 · Calif. Stats. 1851, 2d sess., ch. 14, sec. 29/p. 179
1856
Lost territory Colusi (now Colusa) lost to creation of Tehama.
to Tehama
9 April 1856 · Calif. Stats. 1856, 7th sess., ch. 100/pp. 118-119
1856
Gained territory Colusi (now Colusa) gained from Butte, Sutter, and Yolo.
from Butte from Sutter from Yolo
19 April 1856 · Calif. Stats. 1856, 7th sess., ch. 105/p. 124
1857
Gained territory Colusi (now Colusa) gained from Tehama.
from Tehama
19 February 1857 · Calif. Stats. 1857, 8th sess., ch. 37/p. 25

Show all 14 changes (9 more)

1850
Colusa County created Colusi (now Colusa) created from non-county area; Colusi not fully organized, attached to Butte "for judicial purposes."
from Butte
18 February 1850 · Calif. Stats. 1849, 1st sess., ch. 15, sec. 22/p. 62
1851
Changed Colusi (now Colusa) fully organized, detached from Butte.
Butte
10 January 1851 · Rogers, 57-61
1851
Gained territory Colusi (now Colusa) gained from Yolo, lost to Shasta.
from Yolo from Shasta
25 April 1851 · Calif. Stats. 1851, 2d sess., ch. 14, sec. 29/p. 179
1856
Lost territory Colusi (now Colusa) lost to creation of Tehama.
to Tehama
9 April 1856 · Calif. Stats. 1856, 7th sess., ch. 100/pp. 118-119
1856
Gained territory Colusi (now Colusa) gained from Butte, Sutter, and Yolo.
from Butte from Sutter from Yolo
19 April 1856 · Calif. Stats. 1856, 7th sess., ch. 105/p. 124
1857
Gained territory Colusi (now Colusa) gained from Tehama.
from Tehama
19 February 1857 · Calif. Stats. 1857, 8th sess., ch. 37/p. 25
1859
Changed By January 1859, the spelling of "Colusi" changed to "Colusa."
Colusi
1 January 1859 · Calif. Stats. 1859, 10th sess.; [Green], 44-45
1859
Lost territory Colusa lost to Tehama.
to Tehama
19 April 1859 · Calif. Stats. 1859, 10th sess., ch. 322/p. 359
1868
Lost territory Colusa lost to Lake.
to Lake
24 March 1868 · Calif. Stats. 1867, 17th sess., ch. 257/p. 269
1873
Gained territory Colusa gained from Tehama, lost to Butte.
from Tehama from Butte
1 January 1873 · Political Code 1872, 1: secs. 3915-3916, 3922/pp. 118-119, 123-124
1891
Lost territory Colusa lost small area to Sutter.
to Sutter
31 March 1891 · Calif. Stats. 1891, 29th sess., ch. 240/p. 455
1891
Lost territory Colusa lost to creation of Glenn. Act passed 11 March 1891; referendum for or against creation of the new county held 5 May 1891.
to Glenn
5 May 1891 · Calif. Stats. 1891, 29th sess., ch. 94/pp. 98-101
1893
Gained territory Colusa gained from Glenn.
from Glenn
11 March 1893 · Calif. Stats. 1893, 30th sess., ch. 141/p. 158
1909
Boundary clarified Boundary of Lake with Colusa and Mendocino redefined (no change).
with Lake with Mendocinono change
13 March 1909 · Calif. Stats. 1909, 38th sess., ch. 211/pp. 326-328

Land and parcels

What the maps cover in Colusa

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

Parcels Good enough

Lot lines and tax-map numbers for 15,056 parcels from Colusa County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 31 August 2026 · checked 15 October 2026
Address points Missing

No public address points layer found for Colusa 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

Colusa by the Census

Population

21,839 2020 Census count

Housing units

8,099 2020 Census count

Land area

1,151 square miles

Water area

5.6 square miles

People per sq mi

19 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

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

Inside a city or town, permits usually come from that city rather than the county.

Records

Assessor and property recordsfrom countyofcolusaca.gov · checked 13 October 2026
Clerk of court: deeds and platsfrom countyofcolusaca.gov · checked 13 October 2026

Permits

Health department: septic and well
Behavioral Health
from countyofcolusaca.gov · checked 13 October 2026
Building Permitsfrom countyofcolusaca.gov
Septicfrom countyofcolusaca.gov
Water Wellsfrom countyofcolusaca.gov

Zoning and code

Planning and zoningfrom countyofcolusaca.gov · checked 13 October 2026
Fee Ordinancefrom countyofcolusaca.gov
County Code & Ordinancesfrom countyofcolusaca.gov
Zoningfrom countyofcolusaca.gov
Rezoningfrom countyofcolusaca.gov

County government

County government
The official website of Colusa County.
countyofcolusaca.gov

See your own lot on these maps

Open Colusa 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 Colusa County

When was Colusa County founded?: Colusa County was founded in 1850, formed from Butte County, and named after Rancho Colus, California.
What is the county seat of Colusa County?: The county seat of Colusa County is Colusa.
Is there an online parcel map for Colusa County?: Yes. Colusa County publishes a parcel map of 15,056 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Colusa County's boundary or name changed?: Colusa County was created in 1850 from Butte County. Since then the Atlas of Historical County Boundaries records 12 later changes, chiefly involving Tehama County, Butte County and Glenn County.
Who issues building permits in Colusa County?: The county's page on building permits: Building Permits. Inside a city or town, ask that city first.
Who issues septic and well permits in Colusa County?: The county's page on septic systems and wells: Behavioral Health.
Is my lot in a flood zone?: We do not have flood maps for Colusa County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

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