Black Diamond, WA: Smallest Incorporated City by Population (2010 Census)

Population Ranking

According to the 2010 U.S. Census, Black Diamond (King County) had a population of 4,106, making it the smallest incorporated city in Washington State at that time.

Context

• Located 25 miles SE of Seattle, historic coal-mining town.
• 2020 Census: 6,200+ (growth from Master Planned Developments).
• Other tiny WA cities: Krupp (48), Lamont (70), Wilson Creek (200) – but these are towns (under 1,500). "City" classification in WA requires ≥1,500 population at incorporation; Black Diamond is the smallest city.

Community Character

Known for "small town with a big heart": strong volunteerism, historic museum, mountain bike trails, gateway to Green River Gorge.

Note

Population rankings shift with each census; verify with latest OFM (Office of Financial Management) estimates for current status.