When was Mason County founded?

Mason County was founded in 1854, formed from King County and Thurston County, and named after Charles H. Mason.

What is the county seat of Mason County?

The county seat of Mason County is Shelton.

Is there an online parcel map for Mason County?

Yes. A public source publishes a parcel map of 60,551 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Mason County's boundary or name changed?

Mason County was created in 1854 from King County and Thurston County. Since then the Atlas of Historical County Boundaries records 12 later changes, chiefly involving Kitsap County, Chehalis County and Grays Harbor County. It was formerly called Sawamish.

Who issues building permits in Mason County?

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

Is my lot in a flood zone?

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

County · code 53045

Mason CountyWashington

Mason County is a Washington county of 959.5 square miles, with its seat in Shelton. It was created in 1854 as Sawamish County from King and Thurston counties, and renamed Mason in 1864.

Founded1854
County seatShelton
Named forCharles H. Mason
Land area960 sq mi + 91 sq mi water
Population65,726 2020 Census
Parcels mapped60,551 checked 15 October 2026

Open the free map Click any parcel in Mason 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 King County and Thurston County

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

Originally called Sawamish County, it was created by Washington Territory on March 13, 1854, from parts of King and Thurston counties. The county experienced multiple boundary adjustments with neighboring counties including Kitsap, Thurston, Chehalis, and Jefferson throughout the 1850s and 1860s. On January 24, 1864, Sawamish County was renamed Mason County. Mason County continued as a Washington county when Washington was admitted to the Union on November 11, 1889.

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

1854
Mason County created Sawamish (now Mason) created by Washington Territory from King and Thurston.
from King from Thurston
13 March 1854 · Wash. Terr. Laws 1854, 1st sess., p. 474
1858
Gained territory Sawamish (now Mason) implicitly gained from Kitsap when the south line of Kitsap was redefined.
from Kitsap
13 January 1858 · Wash. Terr. Laws 1857, 5th sess., pp. 51-52
1860
Lost territory Sawamish (now Mason) lost to Chehalis (now Grays Harbor).
to Chehalisto Grays Harbor
25 January 1860 · Wash. Terr. Laws 1859, 7th sess., p. 444
1864
Renamed Sawamish renamed Mason.
formerly Sawamish
8 January 1864 · Wash. Terr. Laws 1863-1864, 11th sess., p. 71
1889
Became part of Washington Mason continued as a Washington county when the state of Washington 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 13 changes (8 more)

1854
Mason County created Sawamish (now Mason) created by Washington Territory from King and Thurston.
from King from Thurston
13 March 1854 · Wash. Terr. Laws 1854, 1st sess., p. 474
1858
Gained territory Sawamish (now Mason) implicitly gained from Kitsap when the south line of Kitsap was redefined.
from Kitsap
13 January 1858 · Wash. Terr. Laws 1857, 5th sess., pp. 51-52
1860
Lost territory Sawamish (now Mason) lost to Chehalis (now Grays Harbor).
to Chehalisto Grays Harbor
25 January 1860 · Wash. Terr. Laws 1859, 7th sess., p. 444
1860
Gained territory Sawamish (now Mason) gained from Thurston.
from Thurston
30 January 1860 · Wash. Terr. Laws 1859, 7th sess., p. 458
1861
Exchanged territory Sawamish (now Mason) exchanged with Thurston.
with Thurston
24 January 1861 · Wash. Terr. Laws 1860, 8th sess., p. 30
1861
Gained territory Sawamish (now Mason) gained from Kitsap.
from Kitsap
30 January 1861 · Wash. Terr. Laws 1860, 8th sess., p. 56
1863
Exchanged territory Sawamish (now Mason) exchanged with Thurston.
with Thurston
28 January 1863 · Wash. Terr. Laws 1862, 10th sess., p. 7
1864
Renamed Sawamish renamed Mason.
formerly Sawamish
8 January 1864 · Wash. Terr. Laws 1863-1864, 11th sess., p. 71
1864
Lost territory Mason lost to Chehalis (now Grays Harbor).
to Chehalisto Grays Harbor
30 January 1864 · Wash. Terr. Laws 1863-1864, 11th sess., p. 74
1867
Gained territory Mason gained from Jefferson, lost to Chehalis (now Grays Harbor), Kitsap, and Thurston.
from Jefferson from Chehalis from Grays Harbor from Kitsapfrom Thurston
31 January 1867 · Wash. Terr. Laws 1866-1867, 14th sess., pp. 45-46
1869
Gained territory Mason gained from Kitsap.
from Kitsap
2 December 1869 · Wash. Terr. Laws 1869, 2nd biennial sess., sec. 1/p. 293
1877
Gained territory Mason gained from Chehalis (now Grays Harbor), Jefferson, and Kitsap.
from Chehalis from Grays Harbor from Jeffersonfrom Kitsap
9 November 1877 · Wash. Terr. Laws 1877, 6th biennial sess., pp. 406-407
1889
Became part of Washington Mason continued as a Washington county when the state of Washington 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 Mason

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

Parcels Good enough

Lot lines and tax-map numbers for 60,551 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 Mason 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

Mason by the Census

Population

65,726 2020 Census count

Housing units

33,269 2020 Census count

Land area

960 square miles

Water area

91 square miles

People per sq mi

68 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.

Permits

Permit Fee Schedulefrom dms.masoncountywa.gov
Respond To Your Septic Deficiency Letterfrom hub.masoncountywa.gov
Sewage / Septicfrom masoncountywa.gov
Access Permitsfrom masoncountywa.gov
Utility Permit Notificationfrom masoncountywa.gov

Zoning and code

Resolutions and Ordinancesfrom dms.masoncountywa.gov
ORV Ordinancefrom dms.masoncountywa.gov
County Zoning (Development Areas)from arcgis.com
Shelton Urban Growth Area Zoningfrom arcgis.com

County government

County government
The official website of Mason County.
masoncountywa.gov

See your own lot on these maps

Open Mason 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 Mason County

When was Mason County founded?: Mason County was founded in 1854, formed from King County and Thurston County, and named after Charles H. Mason.
What is the county seat of Mason County?: The county seat of Mason County is Shelton.
Is there an online parcel map for Mason County?: Yes. A public source publishes a parcel map of 60,551 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Mason County's boundary or name changed?: Mason County was created in 1854 from King County and Thurston County. Since then the Atlas of Historical County Boundaries records 12 later changes, chiefly involving Kitsap County, Chehalis County and Grays Harbor County. It was formerly called Sawamish.
Who issues building permits in Mason County?: The county's page on building permits: Permit Fee Schedule. Inside a city or town, ask that city first.
Is my lot in a flood zone?: We do not have flood maps for Mason County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby