Black Diamond city, Washington
Official LSAD Designation: Black Diamond city • Census GEOID: 5306330
• King County
Black Diamond city is an incorporated city in King County, Washington. According to official records from the Census (2025), Black Diamond city had an estimated population of 6,978 residents. Official Census Bureau geographic records classify this community under LSAD designation Black Diamond city (GEOID 5306330).
Local Government Administration U.S. Census Bureau GMAF
Town Of Black Diamond
Municipal
Official Title:
Mayor
Address:
PO BOX 599, BLACK DIAMOND WA 98010-0599
County Of King
County
Official Title:
Demographer
Address:
401 5TH AVE, STE 800, SEATTLE WA 98104-2391
Civic & Statistical Snapshot
| Category | Estimate | Survey Period / Source |
|---|---|---|
| Total Population | 6,978 | 2025 |
| Median Household Income | $141,383 | 2020-2024 |
| Median Home Value | $779,100 | 2020-2024 |
| Land Area | 6.60 sq mi | Gazetteer (2026) |
| Civic & Public Services | Hospitals, Libraries, Colleges | CMS / IMLS / IPEDS |
| Schools & Districts | NCES Directory Listings | Provided by k12guides.com |
| Nearby Airports | Landing Facilities | Provided by airport-data.com |
| Climate & Weather | NOAA 30-Year Normals | 1991–2020 |
Source: U.S. Census Bureau (PEP, ACS 5-Year).