Auburn is a city in King County, Washington, United States (with a small portion crossing into neighboring Pierce County). The population was 70,180 at the 2010 United States Census. Auburn is a suburb in the Seattle metropolitan area, and is currently ranked as the 15th largest city in the state of Washington. Auburn is bordered by the cities of Federal Way, Pacific, and Algona to the west, Sumner to the south, Kent to the north, and unincorporated King County to the east. The Muckleshoot Indian Reservation lies to the south and southeast.

Federal Way is a city in King County, Washington, located within the Seattle metropolitan area. The population was 89,306 at the 2010 census and an estimated 96,289 in 2019. Federal Way is the tenth-largest city in Washington and the fifth-largest in King County, according to the Census Bureau's 2019 population estimate.

Renton is a city in King County, Washington, and an inner-ring suburb of Seattle. Situated 11 miles (18 km) southeast of downtown Seattle, Renton straddles the southeast shore of Lake Washington, at the mouth of the Cedar River. As of 2019, the population of Renton is estimated at 101,751, up from 90,927 at the 2010 census. The city is currently the sixth-largest municipality in greater Seattle and the eighth-largest in Washington state. After a long history as an important salmon fishing area for Native Americans, Renton was first settled by people of European descent in the 1860s. Its early economy was based on coal mining, clay production, and timber export. Today, Renton is best known as the final assembly point for the Boeing 737 family of commercial airplanes, but it is also home to a growing number of well known manufacturing, technology, and healthcare organizations, including Boeing Commercial Airplanes Division, Paccar, Kaiser Permanente, IKEA, Providence Health & Services, UW Medicine, and Wizards of the Coast.

Burien ( BEWR-ee-ən) is a suburban city in King County, Washington, United States, located south of Seattle on Puget Sound. As of the 2010 Census, Burien's population was 33,313, which is a 49.7% increase since incorporation in 1993. An annexation in 2010 increased the city's population significantly, and as of 2019 the population was an estimated 51,500.