ZIP 99403 falls in Asotin County, Washington, where we hold 3,524 parcels measured as septic county-wide and 5,048 on sewer. We do not have a per-ZIP parcel count for this county, so this is the county total, not a count specific to ZIP 99403.
ZCTA 99403 is not entirely inside one county. Land-area share is from the 2020 Census ZCTA-to-county relationship file.
| County | Land in this ZIP | Documents held | On septic (county) | On sewer (county) |
|---|---|---|---|---|
| Asotin County, Washington | 80% | 54 | 3,524 | 5,048 |
| Garfield County, Washington | 20% | — | 778 | 864 |
Land-area overlap is from the 2020 Census Bureau ZCTA5-to-county relationship file, not an estimate of ours. Parcel and document counts are rows we hold, not a survey of every property in the ZIP. Last verified 2026-09-01.
We hold 3,524 parcels measured as septic for Asotin County, Washington as a whole, not broken out by ZIP.
ZIP 99403 spans 2 counties: Asotin County, Washington, Garfield County, Washington.