When was Napa County founded?

Napa County was founded in 1850, and named after Napa, California.

What is the county seat of Napa County?

The county seat of Napa County is Napa.

Is there an online parcel map for Napa County?

Yes. Napa County publishes a parcel map of 51,249 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Napa County's boundary or name changed?

Napa County was created in 1850. Since then the Atlas of Historical County Boundaries records 6 later changes, chiefly involving Lake County, Mendocino County and Solano County.

Is my lot in a flood zone?

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

County · code 06055

Napa CountyCalifornia

Napa County, in California, was created in 1850 with its seat in the city of Napa.

Founded1850
County seatNapa
Named forNapa, California
Land area748 sq mi + 40 sq mi water
Population138,019 2020 Census
Parcels mapped51,249 checked 16 October 2026

Open the free map Click any parcel in Napa 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.

Napa County was created from non-county area on February 18, 1850. Between 1852 and 1855, Napa County gained territory from Mendocino, Solano, and Sonoma counties. Starting in 1861, Lake County was created from and later exchanged territory with Napa County through 1872.

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

1850
Napa County created Napa created from non-county area. 18 February 1850 · Calif. Stats. 1849, 1st sess., ch. 15, sec. 15/p. 61
1852
Gained territory Napa gained from Mendocino.
from Mendocino
16 April 1852 · Calif. Stats. 1852, 3d sess., ch. 116/p. 192
1855
Gained territory Napa gained from Mendocino, Solano, and Sonoma.
from Mendocino from Solano from Sonoma
4 April 1855 · Calif. Stats. 1855, 6th sess., ch. 68/p. 77
1861
Lost territory Napa lost to creation of Lake.
to Lake
20 May 1861 · Calif. Stats. 1861, 12th sess., ch. 498/pp. 560-561
1864
Lost territory Napa lost to Lake.
to Lake
29 February 1864 · Calif. Stats. 1863-1864, 15th sess., ch. 122/p. 111

Show all 8 changes (3 more, mostly small adjustments)

1850
Napa County created Napa created from non-county area. 18 February 1850 · Calif. Stats. 1849, 1st sess., ch. 15, sec. 15/p. 61
1851
Boundary clarified Napa boundaries redefined (no change).
no change
25 April 1851 · Calif. Stats. 1851, 2d sess., ch. 14, sec. 25/p. 178
1852
Gained territory Napa gained from Mendocino.
from Mendocino
16 April 1852 · Calif. Stats. 1852, 3d sess., ch. 116/p. 192
1855
Gained territory Napa gained from Mendocino, Solano, and Sonoma.
from Mendocino from Solano from Sonoma
4 April 1855 · Calif. Stats. 1855, 6th sess., ch. 68/p. 77
1861
Lost territory Napa lost to creation of Lake.
to Lake
20 May 1861 · Calif. Stats. 1861, 12th sess., ch. 498/pp. 560-561
1864
Lost territory Napa lost to Lake.
to Lake
29 February 1864 · Calif. Stats. 1863-1864, 15th sess., ch. 122/p. 111
1868
Lost territory Napa lost small area to Lake.
to Lake
24 March 1868 · Calif. Stats. 1867, 17th sess., ch. 257/p. 269
1872
Gained territory Napa gained from Lake.
from Lake
8 March 1872 · Calif. Stats. 1871, 19th sess., ch. 229/p. 305

Land and parcels

What the maps cover in Napa

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

Parcels Good enough

Lot lines and tax-map numbers for 51,249 parcels from Napa County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 9 October 2026 · checked 16 October 2026
Address points Missing

No public address points layer found for Napa 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

Napa by the Census

Population

138,019 2020 Census count

Housing units

55,448 2020 Census count

Land area

748 square miles

Water area

40 square miles

People per sq mi

184 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

Napa 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 Napa County.
napacounty.gov

See your own lot on these maps

Open Napa 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 Napa County

When was Napa County founded?: Napa County was founded in 1850, and named after Napa, California.
What is the county seat of Napa County?: The county seat of Napa County is Napa.
Is there an online parcel map for Napa County?: Yes. Napa County publishes a parcel map of 51,249 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Napa County's boundary or name changed?: Napa County was created in 1850. Since then the Atlas of Historical County Boundaries records 6 later changes, chiefly involving Lake County, Mendocino County and Solano County.
Is my lot in a flood zone?: We do not have flood maps for Napa County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby