When was Mariposa County founded?

Mariposa County was founded in 1850, and named after Mariposa Creek.

What is the county seat of Mariposa County?

The county seat of Mariposa County is Mariposa.

Is there an online parcel map for Mariposa County?

Yes. A public source publishes a parcel map of 14,338 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Mariposa County's boundary or name changed?

Mariposa County was created in 1850. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Fresno County, Frezno County and Los Angeles County.

Who issues building permits in Mariposa County?

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

Who issues septic and well permits in Mariposa County?

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

Is my lot in a flood zone?

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

County · code 06043

Mariposa CountyCalifornia

Mariposa County is a county in California, formed in 1850 with its seat in Mariposa. The county is named after Mariposa Creek.

Founded1850
County seatMariposa
Named forMariposa Creek
Land area1,449 sq mi + 14 sq mi water
Population17,131 2020 Census
Parcels mapped14,338 checked 16 October 2026

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

Updated 19 October 2026

Census outline · seat marked

History

Founded in 1850

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

Mariposa County was created on February 18, 1850 from non-county area, and initially included territory that would later form multiple surrounding counties. Over the following two decades, Mariposa lost land to the creation of Tulare County in 1852, Merced County in 1855, Fresno County in 1856, and Mono County in 1861, while gaining and losing small amounts of territory to and from neighboring counties.

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

1850
Mariposa County created Mariposa created from non-county area. 18 February 1850 · Calif. Stats. 1849, 1st sess., ch. 15, sec. 28/p. 63
1851
Gained territory Mariposa gained from San Diego, lost to Los Angeles.
from San Diego from Los Angeles
25 April 1851 · Calif. Stats. 1851, 2d sess., ch. 14, sec. 15/pp. 175-176
1852
Lost territory Mariposa lost to creation of Tulare.
to Tulare
20 April 1852 · Calif. Stats. 1852, 3d sess., ch. 153/pp. 240-242
1855
Lost territory Mariposa lost to creation of Merced.
to Merced
19 April 1855 · Calif. Stats. 1855, 6th sess., ch. 104/pp. 125-128
1856
Lost territory Mariposa lost to creation of Frezno (now Fresno).
to Freznoto Fresno
19 April 1856 · Calif. Stats. 1856, 7th sess., ch. 127/pp. 183

Show all 9 changes (4 more)

1850
Mariposa County created Mariposa created from non-county area. 18 February 1850 · Calif. Stats. 1849, 1st sess., ch. 15, sec. 28/p. 63
1851
Gained territory Mariposa gained from San Diego, lost to Los Angeles.
from San Diego from Los Angeles
25 April 1851 · Calif. Stats. 1851, 2d sess., ch. 14, sec. 15/pp. 175-176
1852
Lost territory Mariposa lost to creation of Tulare.
to Tulare
20 April 1852 · Calif. Stats. 1852, 3d sess., ch. 153/pp. 240-242
1855
Lost territory Mariposa lost to creation of Merced.
to Merced
19 April 1855 · Calif. Stats. 1855, 6th sess., ch. 104/pp. 125-128
1856
Lost territory Mariposa lost to creation of Frezno (now Fresno).
to Freznoto Fresno
19 April 1856 · Calif. Stats. 1856, 7th sess., ch. 127/pp. 183
1861
Lost territory Mariposa lost a remnant of territory to creation of Mono.
to Mono
24 April 1861 · Calif. Stats. 1861, 12th sess., ch. 233/pp. 235-236
1870
Gained territory Mariposa gained from Fresno.
from Fresno
29 March 1870 · Calif. Stats. 1869, 18th sess., ch. 341/p. 449
1872
Lost territory Mariposa lost to Fresno.
to Fresno
1 April 1872 · Calif. Stats. 1871, 19th sess., ch. 602/p. 891
1874
Boundary clarified Boundary between Mariposa and Fresno redefined (no change).
with Fresnono change
11 February 1874 · Calif. Stats. 1873, 20th sess., ch. 88/p. 100

Land and parcels

What the maps cover in Mariposa

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

Parcels Good enough

Lot lines and tax-map numbers for 14,338 parcels. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 15 October 2026 · checked 16 October 2026
Address points Missing

No public address points layer found for Mariposa 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

Mariposa by the Census

Population

17,131 2020 Census count

Housing units

9,760 2020 Census count

Land area

1,449 square miles

Water area

14 square miles

People per sq mi

12 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 mariposacounty.gov · checked 14 October 2026
Clerk of court: deeds and plats
Clerk of the Board of Supervisors
from mariposacounty.gov · checked 14 October 2026

Permits

Health department: septic and wellfrom mariposacounty.gov · checked 14 October 2026
Permitsfrom mariposacounty.gov
Archive Center • Building Permits Issuedfrom mariposacounty.gov
Water Wellsfrom mariposacounty.gov
So Now You Own a Septic System Brochure (PDF)from mariposacounty.gov

Zoning and code

Planning and zoningfrom mariposacounty.gov · checked 14 October 2026
Ordinancesfrom mariposacounty.gov
Ordinancesfrom mariposacounty.gov
Public Zoning Lookup Toolfrom mariposacounty.gov

County government

County government
The official website of Mariposa County.
mariposacounty.gov

See your own lot on these maps

Open Mariposa 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 Mariposa County

When was Mariposa County founded?: Mariposa County was founded in 1850, and named after Mariposa Creek.
What is the county seat of Mariposa County?: The county seat of Mariposa County is Mariposa.
Is there an online parcel map for Mariposa County?: Yes. A public source publishes a parcel map of 14,338 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Mariposa County's boundary or name changed?: Mariposa County was created in 1850. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Fresno County, Frezno County and Los Angeles County.
Who issues building permits in Mariposa County?: The county's page on building permits: Permits. Inside a city or town, ask that city first.
Who issues septic and well permits in Mariposa County?: The county's page on septic systems and wells: Behavioral Health and Recovery Services.
Is my lot in a flood zone?: We do not have flood maps for Mariposa 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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