Query: By what time was Seattle the most rapidly growing city in the US?
Context: With an estimated 662,400 residents as of 2015[update], Seattle is the largest city in both the state of Washington and the Pacific Northwest region of North America. In July 2013 it was the fastest-growing major city in the United States, and remained in the top five in May 2015 with an annual growth rate of 2.1%. The Seattle metropolitan area of around 3.6 million inhabitants is the 15th largest metropolitan area in the United States.