International immigration has driven King County’s population growth since Seattle’s tech boom took off in the 2010s. Over that decade, the county grew by about 159,000 people through international immigration, while domestic migration added less than a third of that — about 44,000.

That pattern has only intensified. From 2020 to 2025, international immigration added about 132,000 people to King County, while domestic migration reversed entirely, falling by 95,000.

That growth isn’t spread evenly. Comparing the most recent census tract data, from 2024, with 2015 figures shows where the biggest surges happened.

The concentration is in two places: the Eastside’s suburban tech corridor and Seattle’s high-density urban core. Different as they are, both share a profile — immigrants mostly from Asian countries, and a large share of tech workers.

Issaquah Highlands saw the biggest gain. Its foreign-born population surged from fewer than 500 in 2015 to nearly 3,600 in 2024 — this was the only tract in King County where the immigrant population increased by more than 3,000. Nearly three in four of those people were born in an Asian country. In 2024, the foreign-born population made up more than 40% of the tract.

It’s an affluent area, with a median household income of about $170,000. More than 70% of adults held a bachelor’s degree, and more than one in five full-time employed residents worked in tech.

The next two biggest surges came from established Eastside job centers. A fast-growing tract in downtown Redmond, which includes Redmond Town Center, added 2,500 foreign-born residents, climbing from around 700 in 2015 to 3,200 in 2024. Immigrants now make up nearly half (48%) of the tract’s population, with two-thirds from Asian countries. Thirty-eight percent of full-time workers here are in tech, fitting for Microsoft’s hometown.

Nearby, the Overlake neighborhood on the Bellevue-Redmond border — home to Microsoft’s East Campus — saw its immigrant population grow by about 2,300. That’s notable because Overlake was already majority-immigrant a decade ago. By 2024, about 5,600 residents were foreign-born, 65% of the tract, with more than 80% of immigrants there from Asian countries. Nearly half of full-time workers — 48% — worked in tech.

The remaining two top-five tracts sit in Seattle’s urban core, near the Amazon campus. The eastern half of Belltown, spilling into the Denny Triangle, gained more than 2,200 foreign-born residents — pushing the tract just past the halfway mark and making it one of the few majority-immigrant areas in Seattle proper. A decade ago, only around 300 foreign-born residents lived here; by 2024 that number reached 2,500. Three in four were born in an Asian country, and 36% of full-time workers are in tech.

A nearby tract covering the eastern part of Denny Triangle added about 2,100 immigrant residents, growing from under 500 to more than 2,500 — just under half the population, with more than 80% from Asian countries. Tech workers made up 51% of the full-time workforce here, the highest share of any tract on the list.

These five census tracts were the only ones among King County’s 495 tracts where the immigrant population increased by more than 2,000 from 2015 to 2024. Another six tracts — five on the Eastside and one in Kent — saw increases between 1,500 and 2,000.

Because this census data only captures population shifts through the end of 2024, the regional impact of the Trump administration’s stricter immigration enforcement on these trends remains to be seen.

A note on the census data: In order to increase accuracy, the Census Bureau averages five years of survey data for each release of census tract data. For the 2024 data, the numbers average 2020 to 2024, and for the 2015 data, they average 2011 to 2015.