Seattle is the county seat of King County, in the state of Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Pacific Northwest region of North America and the largest city on the West Coast north of San Francisco. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the United States. The city is a major coastal seaport situated on a narrow isthmus between Puget Sound (an arm of the Pacific Ocean) and Lake Washington, about 114 miles (183 km) south of the Canada–United States border. In 2010, Seattle was the sixth busiest port in the United States, serving as a major gateway for trade with Asia.