5,761 residents live across 11 ZIPs covering 936 sq mi, served by 11 distinct USPS-recognized cities.
Population moved from 5,946 to 5,761 from 2014 to 2024 — a -3.1% change. 4 ZIPs gained residents, 7 lost.
The county's wealthiest ZIP 66958 (Morrowville, $77,750 median) and poorest ZIP 66946 (Hollenberg, $53,542) are 10.3 miles apart — a 1.5× income gap across local geography.
Median home values vary 4.0× across this county — from $75,000 in 66958 (Morrowville) to $303,700 in 66962 (Palmer).
Density varies 4× across the county — from 3 people/sq mi in 66958 (Morrowville) to 11 in 66945 (Hanover).
Educational attainment ranges from 15.6% bachelor's+ in 66933 (Barnes) to 52.7% in 66944 (Haddam) — the breadth of educational profiles across the area.
Within Kansas, this is the #106 most populous of 106 counties and ranks #4 for median household income .
Weighted by population, the typical household earns about $65,469 across the county — reflecting what a typical resident sees, not a simple ZIP average.
25.8% of adults age 25+ hold a bachelor's degree or higher (1,047 of 4,054 reporting).
11 Standard delivery, 0 PO Box only, 0 single-entity Unique ZIPs serve this county.
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.
Washington County lost 39.7% of residents between 2014 and 2024. ZIPs that shed the largest share:
| ZIP | City | Type | Population | Median Income | Area (sq mi) | 10-yr Growth |
|---|---|---|---|---|---|---|
| 66968 | Washington | Standard | 1,454 | $59,438 | 136.6 | -17.0% |
| 66945 | Hanover | Standard | 1,063 | $69,688 | 96.7 | 15.9% |
| 66937 | Clifton | Standard | 691 | $63,456 | 136.8 | -12.1% |
| 66953 | Linn | Standard | 628 | $66,250 | 73.0 | -6.8% |
| 66943 | Greenleaf | Standard | 568 | $67,738 | 93.0 | 13.1% |
| 66933 | Barnes | Standard | 345 | $55,625 | 87.7 | 21.5% |
| 66944 | Haddam | Standard | 304 | $75,625 | 94.3 | 92.4% |
| 66962 | Palmer | Standard | 302 | $74,583 | 52.1 | -3.5% |
| 66958 | Morrowville | Standard | 198 | $77,750 | 73.1 | -36.9% |
| 66946 | Hollenberg | Standard | 161 | $53,542 | 51.7 | -4.2% |
| 66955 | Mahaska | Standard | 47 | $85,500 | 40.6 | -39.7% |