When was Columbia County founded?

Columbia County was founded in 1854, formed from Washington County, and named after Columbia River.

What is the county seat of Columbia County?

The county seat of Columbia County is St. Helens.

Is there an online parcel map for Columbia County?

Yes. Columbia County publishes a parcel map of 28,843 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Columbia County's boundary or name changed?

Columbia County was created in 1854 from Washington County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Multnomah County, Washington County and Clatsop County.

Is my lot in a flood zone?

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

County · code 41009

Columbia CountyOregon

Columbia County is a county in Oregon with its seat in St. Helens. The county was created on January 16, 1854, and named after the Columbia River.

Founded1854
County seatSt. Helens
Named forColumbia River
Land area659 sq mi + 30 sq mi water
Population52,589 2020 Census
Parcels mapped28,843 checked 15 October 2026

Open the free map Click any parcel in Columbia 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 Washington County

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

Columbia County was created by Oregon Territory on January 16, 1854, from Washington. It went through multiple boundary adjustments over the following decades, gaining and losing territory to neighboring counties including Clatsop, Multnomah, and Washington. Columbia County became an Oregon county in 1859 when the state of Oregon was admitted to the Union and Oregon Territory was eliminated.

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

1854
Columbia County created Columbia created by Oregon Territory from Washington.
from Washington
16 January 1854 · Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 32-33
1855
Gained territory Columbia's western boundary defined; gained from Clatsop.
from Clatsop
15 January 1855 · Ore. Terr. Special Laws 1854, 6th reg. sess., p. 34
1859
Became part of Oregon Columbia became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. 14 February 1859 · U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30
1864
Lost territory Columbia lost to Multnomah.
to Multnomah
24 October 1864 · Ore. Laws 1864, 3rd reg. sess., p. 62
1898
Lost territory Columbia lost to Washington.
to Washington
15 October 1898 · Ore. Laws 1898, 20th spec. sess., pp. 27-28

Show all 9 changes (4 more)

1854
Columbia County created Columbia created by Oregon Territory from Washington.
from Washington
16 January 1854 · Ore. Terr. Special Laws 1853, 5th reg. sess., pp. 32-33
1855
Gained territory Columbia's western boundary defined; gained from Clatsop.
from Clatsop
15 January 1855 · Ore. Terr. Special Laws 1854, 6th reg. sess., p. 34
1859
Became part of Oregon Columbia became an Oregon county when the state of Oregon was admitted to the Union and Oregon Territory was eliminated. 14 February 1859 · U.S. Stat., vol. 11, ch. 33[1859], secs. 1-2/pp. 383-384; Ore. Laws 1860, 1st reg. sess., pp. 28-30
1864
Lost territory Columbia lost to Multnomah.
to Multnomah
24 October 1864 · Ore. Laws 1864, 3rd reg. sess., p. 62
1885
Boundary clarified Columbia boundaries redefined; exchanged with Washington, lost to Clatsop and Multnomah.
with Washington with Clatsop with Multnomahno change
24 February 1885 · Ore. Special Laws 1885, 13th reg. sess., p. 324
1898
Lost territory Columbia lost to Washington.
to Washington
15 October 1898 · Ore. Laws 1898, 20th spec. sess., pp. 27-28
1901
Gained territory Columbia gained from Washington, exchanged with Multnomah.
from Washington from Multnomah
25 February 1901 · Ore. Laws 1901, 21st reg. sess., pp. 126-127
1903
Lost territory Columbia lost to Washington.
to Washington
21 February 1903 · Ore. Laws 1903, 22nd reg. sess., pp. 151-152
1931
Gained territory Columbia gained from Multnomah, lost to Clatsop when boundary was redefined to run along range line.
from Multnomah from Clatsop
6 March 1931 · Ore. Laws 1931, gen., 36th reg. sess., ch. 289/p. 515

Land and parcels

What the maps cover in Columbia

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

Parcels Good enough

Lot lines and tax-map numbers for 28,843 parcels from Columbia County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 15 October 2026
Address points Official

One point per address, 23,967 in all from State of Oregon — Department of Administrative Services Geospatial Enterprise Office (GEOHub) with Oregon Department of Emergency Management 9-1-1 program.
edited 16 January 2026 · checked 13 October 2026
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

Columbia by the Census

Population

52,589 2020 Census count

Housing units

21,697 2020 Census count

Land area

659 square miles

Water area

30 square miles

People per sq mi

80 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

Columbia 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 Columbia County.
co.columbia.or.us

See your own lot on these maps

Open Columbia 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 Columbia County

When was Columbia County founded?: Columbia County was founded in 1854, formed from Washington County, and named after Columbia River.
What is the county seat of Columbia County?: The county seat of Columbia County is St. Helens.
Is there an online parcel map for Columbia County?: Yes. Columbia County publishes a parcel map of 28,843 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Columbia County's boundary or name changed?: Columbia County was created in 1854 from Washington County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Multnomah County, Washington County and Clatsop County.
Is my lot in a flood zone?: We do not have flood maps for Columbia County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby