When was Thurston County founded?

Thurston County was founded in 1852, formed from Clark County and Lewis County, and named after Samuel Thurston.

What is the county seat of Thurston County?

The county seat of Thurston County is Olympia.

Is there an online parcel map for Thurston County?

Yes. A public source publishes a parcel map of 130,363 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Thurston County's boundary or name changed?

Thurston County was created in 1852 from Clark County and Lewis County. Since then the Atlas of Historical County Boundaries records 13 later changes, chiefly involving Mason County, Sawamish County and Chehalis County.

Is my lot in a flood zone?

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

County · code 53067

Thurston CountyWashington

Thurston County is a county in Washington, with its seat in Olympia. It was created on January 12, 1852, as part of Oregon Territory from Clark and Lewis counties, and was named after Samuel Thurston.

Founded1852
County seatOlympia
Named forSamuel Thurston
Land area723 sq mi + 52 sq mi water
Population294,793 2020 Census
Parcels mapped130,363 checked 15 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1852 from Clark County and Lewis County

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

Thurston County was created by Oregon Territory on January 12, 1852, from Clark and Lewis counties, and initially included the disputed San Juan Islands claimed by both the United States and Great Britain until 1872. The county became part of Washington Territory on March 2, 1853, and its boundaries changed multiple times through the creation of neighboring counties including Island, Jefferson, King, Pierce, Mason, and Grays Harbor.

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

1852
Thurston County created Thurston created by Oregon Territory from Clark and Lewis. Thurston included the disputed San Juan Islands which were claimed by both the United States and Great Britain.
from Clark from Lewis
12 January 1852 · Ore. Terr. Laws 1851, 3rd reg. sess., p. 19
1852
Lost territory Thurston lost to creation of Island, Jefferson, King and Pierce.
to Island to Jefferson to King to Pierce
22 December 1852 · Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 41-47
1853
Lost territory Thurston lost to Lewis.
to Lewis
1 February 1853 · Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40
1853
Became part of Washington Thurston became a county in Washington Territory; eliminated from Oregon Territory. 2 March 1853 · Wash. Terr. Laws, 1854, 1st. sess., p. 32; Van Zandt, 155
1854
Lost territory Thurston lost to creation of Sawamish (now Mason), and lost to King.
to Sawamish to Masonto King
13 March 1854 · Wash. Terr. Laws 1854, 1st sess., p. 474

Show all 15 changes (10 more)

1852
Thurston County created Thurston created by Oregon Territory from Clark and Lewis. Thurston included the disputed San Juan Islands which were claimed by both the United States and Great Britain.
from Clark from Lewis
12 January 1852 · Ore. Terr. Laws 1851, 3rd reg. sess., p. 19
1852
Lost territory Thurston lost to creation of Island, Jefferson, King and Pierce.
to Island to Jefferson to King to Pierce
22 December 1852 · Ore. Terr. Special Laws 1852, 4th reg. sess., pp. 41-47
1853
Lost territory Thurston lost to Lewis.
to Lewis
1 February 1853 · Ore. Terr. Special Laws 1852, 4th reg. sess., p. 40
1853
Became part of Washington Thurston became a county in Washington Territory; eliminated from Oregon Territory. 2 March 1853 · Wash. Terr. Laws, 1854, 1st. sess., p. 32; Van Zandt, 155
1854
Lost territory Thurston lost to creation of Sawamish (now Mason), and lost to King.
to Sawamish to Masonto King
13 March 1854 · Wash. Terr. Laws 1854, 1st sess., p. 474
1854
Lost territory Thurston lost to creation of Chehalis (now Grays Harbor).
to Chehalisto Grays Harbor
14 April 1854 · Wash. Terr. Laws 1854, 1st sess., p. 472
1859
Lost territory Thurston lost to Pierce.
to Pierce
29 January 1859 · Wash. Terr. Laws 1858, 6th sess., p. 59
1860
Lost territory Thurston lost to Chehalis (now Grays Harbor).
to Chehalisto Grays Harbor
25 January 1860 · Wash. Terr. Laws 1859, 7th sess., p. 444
1860
Lost territory Thurston lost to Sawamish (now Mason).
to Sawamishto Mason
30 January 1860 · Wash. Terr. Laws 1859, 7th sess., p. 458
1861
Exchanged territory Thurston exchanged with Sawamish (now Mason).
with Sawamishwith Mason
24 January 1861 · Wash. Terr. Laws 1860, 8th sess., p. 30
1861
Exchanged territory Thurston exchanged with Lewis.
with Lewis
26 January 1861 · Wash. Terr. Laws 1860, 8th sess., p. 33
1863
Exchanged territory Thurston exchanged with Sawamish (now Mason).
with Sawamishwith Mason
28 January 1863 · Wash. Terr. Laws 1862, 10th sess., p. 7
1867
Gained territory Thurston gained from Mason, lost to Lewis.
from Mason from Lewis
31 January 1867 · Wash. Terr. Laws 1866-1867, 14th sess., pp. 47-48
1869
Boundary clarified Thurston redefined (no change).
no change
2 December 1869 · Wash. Terr. Laws 1869, 2nd biennial sess., sec. 1/pp. 294-295
1873
Gained territory Thurston gained from Chehalis (now Grays Harbor).
from Chehalisfrom Grays Harbor
10 November 1873 · Wash. Terr. Laws 1873, 4th biennial sess., pp. 482-483

Land and parcels

What the maps cover in Thurston

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

Parcels Good enough

Lot lines and tax-map numbers for 130,363 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 Thurston 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

Thurston by the Census

Population

294,793 2020 Census count

Housing units

121,438 2020 Census count

Land area

723 square miles

Water area

52 square miles

People per sq mi

408 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

Thurston 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 Thurston County.
thurstoncountywa.gov

See your own lot on these maps

Open Thurston 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 Thurston County

When was Thurston County founded?: Thurston County was founded in 1852, formed from Clark County and Lewis County, and named after Samuel Thurston.
What is the county seat of Thurston County?: The county seat of Thurston County is Olympia.
Is there an online parcel map for Thurston County?: Yes. A public source publishes a parcel map of 130,363 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Thurston County's boundary or name changed?: Thurston County was created in 1852 from Clark County and Lewis County. Since then the Atlas of Historical County Boundaries records 13 later changes, chiefly involving Mason County, Sawamish County and Chehalis County.
Is my lot in a flood zone?: We do not have flood maps for Thurston County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby