When was Cowlitz County founded?

Cowlitz County was founded in 1854, formed from Lewis County, and named after Cowlitz people.

What is the county seat of Cowlitz County?

The county seat of Cowlitz County is Kelso.

Is there an online parcel map for Cowlitz County?

Yes. A public source publishes a parcel map of 57,512 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Cowlitz County's boundary or name changed?

Cowlitz County was created in 1854 from Lewis County. Since then the Atlas of Historical County Boundaries records 6 later changes, chiefly involving Clarke County, Wahkiakum County and Lewis County.

Who issues building permits in Cowlitz 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 Cowlitz County?

The county's page on septic systems and wells: Health* *Ask Cowlitz.

Is my lot in a flood zone?

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

County · code 53015

Cowlitz CountyWashington

Cowlitz County is a Washington county with its seat in Kelso, covering 1,141 square miles. It was created in 1854 from Lewis County and named after the Cowlitz people.

Founded1854
County seatKelso
Named forCowlitz people
Land area1,141 sq mi + 25 sq mi water
Population110,730 2020 Census
Parcels mapped57,512 checked 15 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1854 from Lewis County

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

Cowlitz County was created by Washington Territory on April 21, 1854, from Lewis County, then lost territory four days later to the creation of Wahkiakum County. It underwent several boundary adjustments with Lewis and Clarke counties over the following decades, continuing as a Washington county when the state was admitted to the Union in 1889.

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

1854
Cowlitz County created Cowlitz created by Washington Territory from Lewis.
from Lewis
21 April 1854 · Wash. Terr. Laws 1854, 1st sess., p. 471
1854
Lost territory Cowlitz lost to creation of Wahkiakum.
to Wahkiakum
25 April 1854 · Wash. Terr. Laws 1854, 1st sess., p. 474
1855
Gained territory Cowlitz gained from Lewis and Wahkiakum.
from Lewis from Wahkiakum
26 January 1855 · Wash. Terr. Laws 1854, 2nd sess., p. 36
1867
Lost territory Cowlitz lost to Clarke.
to Clarke
31 January 1867 · Wash. Terr. Laws 1866-1867, 14th sess., p. 48
1889
Became part of Washington Cowlitz continued as a Washington county when the state of Washington was admitted to the Union and Washington Territory eliminated. 11 November 1889 · U.S. Stat., vol. 25, ch. 180[1889], p. 676; U.S. Stat. pres. proc., vol. 26[1889], p. 10; Van Zandt, 155-156

Show all 8 changes (3 more)

1854
Cowlitz County created Cowlitz created by Washington Territory from Lewis.
from Lewis
21 April 1854 · Wash. Terr. Laws 1854, 1st sess., p. 471
1854
Lost territory Cowlitz lost to creation of Wahkiakum.
to Wahkiakum
25 April 1854 · Wash. Terr. Laws 1854, 1st sess., p. 474
1855
Gained territory Cowlitz gained from Lewis and Wahkiakum.
from Lewis from Wahkiakum
26 January 1855 · Wash. Terr. Laws 1854, 2nd sess., p. 36
1867
Lost territory Cowlitz lost to Clarke.
to Clarke
31 January 1867 · Wash. Terr. Laws 1866-1867, 14th sess., p. 48
1869
Boundary clarified Cowlitz redefined (no change).
no change
2 December 1869 · Wash. Terr. Laws 1869, 2nd biennial sess., sec. 1/p. 295
1871
Gained territory Cowlitz gained from Clarke.
from Clarke
29 November 1871 · Wash. Terr. Laws 1871, 3rd biennial sess., pp. 153-154
1873
Lost territory Cowlitz lost to Clarke.
to Clarke
14 November 1873 · Wash. Terr. Laws 1873, 4th biennial sess., p. 561
1889
Became part of Washington Cowlitz continued as a Washington county when the state of Washington was admitted to the Union and Washington Territory eliminated. 11 November 1889 · U.S. Stat., vol. 25, ch. 180[1889], p. 676; U.S. Stat. pres. proc., vol. 26[1889], p. 10; Van Zandt, 155-156

Land and parcels

What the maps cover in Cowlitz

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

Parcels Good enough

Lot lines and tax-map numbers for 57,512 parcels. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 24 September 2026 · checked 15 October 2026
Address points Missing

No public address points layer found for Cowlitz 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

Cowlitz by the Census

Population

110,730 2020 Census count

Housing units

45,424 2020 Census count

Land area

1,141 square miles

Water area

25 square miles

People per sq mi

97 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 co.cowlitz.wa.us · checked 13 October 2026
Clerk of court: deeds and platsfrom co.cowlitz.wa.us · checked 13 October 2026

Permits

Health department: septic and wellfrom co.cowlitz.wa.us · checked 13 October 2026
Permitsfrom co.cowlitz.wa.us
Catering Permitsfrom co.cowlitz.wa.us
Septic Brochuresfrom co.cowlitz.wa.us
Living with your septic systemfrom co.cowlitz.wa.us

Zoning and code

Planning and zoningfrom co.cowlitz.wa.us · checked 13 October 2026
Zoningfrom co.cowlitz.wa.us

County government

County government
The official website of Cowlitz County.
co.cowlitz.wa.us

See your own lot on these maps

Open Cowlitz 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 Cowlitz County

When was Cowlitz County founded?: Cowlitz County was founded in 1854, formed from Lewis County, and named after Cowlitz people.
What is the county seat of Cowlitz County?: The county seat of Cowlitz County is Kelso.
Is there an online parcel map for Cowlitz County?: Yes. A public source publishes a parcel map of 57,512 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Cowlitz County's boundary or name changed?: Cowlitz County was created in 1854 from Lewis County. Since then the Atlas of Historical County Boundaries records 6 later changes, chiefly involving Clarke County, Wahkiakum County and Lewis County.
Who issues building permits in Cowlitz 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 Cowlitz County?: The county's page on septic systems and wells: Health* *Ask Cowlitz.
Is my lot in a flood zone?: We do not have flood maps for Cowlitz County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby