ZIP 99371 falls in Adams County, Washington, where we hold 2,683 parcels measured as septic county-wide and 3,317 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 99371.
ZCTA 99371 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) |
|---|---|---|---|---|
| Adams County, Washington | 79% | 17 | 2,683 | 3,317 |
| Franklin County, Washington | 21% | — | 3,500 | 21,631 |
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 2,683 parcels measured as septic for Adams County, Washington as a whole, not broken out by ZIP.
ZIP 99371 spans 2 counties: Adams County, Washington, Franklin County, Washington.