ZIP Codes of Columbia County, WA

Population & People
Population & People
Total Population
3,740
Household Income
Household Income
Median Income
$66,878
Housing
Housing
Total Housing Units
2,059
Business & Economy
Business & Economy
Total Businesses
104
Employment
Employment
Employment Rate
52.18%
Education
Education
Bachelor's Degree+
23.25%
Source: U.S. Census ACS 2024 5-Year Estimates · rolled up across the 2 ZIPs in this county.
Data Last Updated: June 1, 2026
ZIP Codes:2 ZIP Codes (1 Standard, 1 PO Box, 0 Unique) [See All]
Area Code:509
Timezone:Pacific (GMT -08:00)
Local Time:2:14:15 PM
Population:3,740 [See All]
FIPS:53013
Land Area:758 sq mi
Water Area:5 sq mi
Coordinates:46.3850, -118.0031
Quick Link:
https://www.zip-codes.com/county/wa-columbia.asp
Need Columbia data in your app? Look up ZIP, county, and city data with a single API call.
Try Free
Washington's #38 most populous county
3,740 residents across 2 ZIPs — #38 of 39 Washington counties.

Standout ZIPs in this County


Most Populous
Dayton · 3,646 people
97.5% of county total
Highest Income
Dayton · $72,756 median
1.1× county average
Largest Land Area
Dayton · 757.7 sq mi
Spans the most ground
Fastest Growth
Dayton · -2.9% (10-yr)
3,753 → 3,646 residents
Most Educated
Dayton · 24.0% bachelor's+
667 of 2,784 adults 25+

Things worth knowing about Columbia County


3,740 residents live across 2 ZIPs covering 758 sq mi, served by 2 distinct USPS-recognized cities.

Population moved from 3,860 to 3,740 from 2014 to 2024 — a -3.1% change. 0 ZIPs gained residents, 2 lost.

The county's wealthiest ZIP 99328 (Dayton, $72,756 median) and poorest ZIP 99359 (Starbuck, $61,000) are 22.0 miles apart — a 1.2× income gap across local geography.

Median home values vary 2.0× across this county — from $135,400 in 99359 (Starbuck) to $272,100 in 99328 (Dayton).

Density varies 110× across the county — from 5 people/sq mi in 99328 (Dayton) to 530 in 99359 (Starbuck).

Educational attainment ranges from 2.1% bachelor's+ in 99359 (Starbuck) to 24.0% in 99328 (Dayton) — the breadth of educational profiles across the area.

Within Washington, this is the #38 most populous of 39 counties and ranks #30 for median household income .

Weighted by population, the typical household earns about $72,461 across the county — reflecting what a typical resident sees, not a simple ZIP average.

23.2% of adults age 25+ hold a bachelor's degree or higher (669 of 2,878 reporting).

1 Standard delivery, 1 PO Box only, 0 single-entity Unique ZIPs serve this county.

Stories about Columbia County


Big & sparse

A frontier county — vast land area with only a few residents per square mile. Daily life looks very different here than in the country's denser counties.

Total area
758
square miles
Avg density
4.9
people per sq mi
Population
3,740
across 2 ZIPs
Dayton
757.7 sq mi
3,646 residents
Starbuck
0.2 sq mi
94 residents

Single-ZIP anchor

One ZIP holds the majority of this county's population — a sign of a county built around a single city or town.

Dayton

All ZIP Codes in Columbia County


ZIPCityTypePopulationMedian IncomeArea (sq mi)10-yr Growth
99328DaytonStandard3,646$72,756757.7-2.9%
99359StarbuckPO Box94$61,0000.2-12.1%

Adjacent & Nearby Counties