Washington counties by area

Understanding Washington’s county areas

The land-area range runs from San Juan County at 173.9 mi² to Okanogan County at 5,266.2 mi². The largest has 30.3 times the land area of the smallest and accounts for 7.9% of the combined county land in Washington. Compare with every state’s largest county.

The median county-equivalent land area is 1,738.8 mi², above the national median of 604.5 mi². The median describes the middle of the county size distribution; it does not describe how people or development are distributed. A state with a few very large counties can have a much smaller median than its largest entry suggests.

Where water changes the picture

Clallam County has the most assigned water area, at 930.2 mi². San Juan County has the highest water share, with water making up 72% of its total area. Water area and water percentage answer different questions: the first measures an amount, while the second measures the mix of land and water.

Across all 39 entries, water accounts for 6.8% of the combined total area. This is calculated from the summed land and water measurements, rather than averaging county percentages, which would give each small and large county equal weight.

Where people live

An estimated 8,001,020 people lived in Washington on July 1, 2025 (+3.8% since 2020), or 2.3% of the national total in this dataset. King County is the most populous county equivalent, with 2,344,939 residents — 29.3% of the state. The largest by land, Okanogan County, has 45,230.

Across the state there are 120 people per square mile of land. County densities range from 1,108 in King County to 3.4 in Garfield County; the median county equivalent has 39. Switch the map above to density to see where the state’s population concentrates.

Compare the largest and smallest county equivalents in Washington to see land, water, and total area on the same scale.

These calculations use the 2026 Census county records listed below. County-equivalent boundaries vary between states; area alone does not measure population, density, or usable land. See coverage and calculation rules.