A growing King County population that increasingly resides in cities.

The overall population of King County has increased from around 1.5 million residents in 1990 to over 2.26 million residents in 2020, an increase of 50%. This was significantly faster than overall U.S. population growth of 32% from 1990 to 2018. During this time period, the number of residents living in unincorporated King County has decreased by more than half.

This trend is due to population growth centered in cities, newly created cities, and annexations of formerly unincorporated areas into cities, a trend further revealed by the population growth in the five largest cities in King County. While Seattle and Bellevue saw healthy population growth, Kent and Renton exploded in terms of population, with increases of 244% and 153%, respectively. Both cities annexed a number of areas in the last 25 years and are adjacent to areas currently identified as potential annexation areas. Furthermore, King County added eight new cities, going from 31 incorporated cities in 1990 to 39 cities in 2018. However, while the population residing in unincorporated areas of King County is on the decline, its population still ranks second behind the City of Seattle. 

King County is increasingly racially and ethnically diverse, although much of the diversity is concentrated in particular areas within the county.

The percentage of white residents in King County decreased between 2000 and 2018. During this period, nearly every minority category saw gains, particularly Asian and Hispanic populations. Asian residents accounted for 18% of the population of King County in 2018, up significantly from 10.8% in 2000. The Hispanic population grew to 9.8% of the King County population in 2018, up from 5.5% in 2000.

The trend in the United States as a whole reveals a shrinking population of white residents from 2000 to 2018; Hispanic and Asian residents both significantly increased their share of the total population in that time period.

A look at the detailed 2010 Census data shows that while King County is quite diverse, much of the diversity is concentrated in particular areas of the County. South Seattle and southwest King County show high concentrations of minority populations, while the easternmost reaches of the county continue to be predominantly white.

A steadily increasing proportion of King County residents are foreign-born.

As King County's population has boomed in recent years, much of the increase has been due to an influx of foreign-born residents. In 2000, 15.4% of King County residents were born in another country. As of 2018, this had grown to 23.5%. Between 2000 and 2018, King County's total population increased by around 496,000 residents. The foreign-born population increased by about 255,000 residents, accounting for 52% of the total population growth. The United States also experienced an increase in foreign-born residents between 2000 and 2018, yet the proportion of the total population only increased slightly. Of the 46 million new US residents between 2000 and 2018, 13.6 million, or 30%, identified as foreign-born.

The origins of foreign-born residents also differ between King County and the United States. Greater than half of the foreign-born residents of King County hail from Asia and one-fifth from the Americas, while for the United States as a whole, 52.2% of foreign-born residents are from the Americas and 31% from Asia. In King County, the most common countries of origin are China including Taiwan and Hong Kong (80,165), India (67,842), and Mexico (52,327 residents). For the United States, the most common countries are the same, but with a much larger proportion from Mexico (11.2 million residents) than China (2.8 million) or India (2.6 million).

Most residents of King County reside in family households.

Even with rapid population growth and changing demographics in terms of countries of origin and racial makeup, the types of households in which King County residents reside have remained largely unchanged since 2000. As of 2018, 60% of King County residents live in family households - married with or without children, or single parent households. About 29% of King County residents live alone, while the remaining 11% live in other non-family household arrangements.

The breakdown of household types is similar for the United States as a whole, although a higher proportion of US residents, 65%, live in family households. Single-parent households are more prevalent in the United States than in King County, while non-family households hold a smaller share of the US population than that of King County.

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Technical Notes

Data for King County, city, and unincorporated area populations via the Washington State Office of Financial Management.

Data for County and US populations by race, foreign-born population, origin of foreign-born residents, and household types was taken from the American Community Survey via the US Census Bureau.

Data updated July 2020

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