Seattle is the most populous city in the U.S. state of Washington and the Pacific Northwest region of North America. It is the 18th-most populous city in the United States with a population of 784,777 in 2025, while the Seattle metropolitan area at over 4.15 million residents is the 15th-most populous metropolitan area in the nation. The city is the county seat of King County, the most populous county in Washington. Seattle's growth rate of 21.1% between 2010 and 2020 made it one of the country's fastest-growing large cities.