Seattle is 2 times larger than Boston.
Area: 129 km2 calculated
Boston is the capital and largest city of the Commonwealth of Massachusetts in the United States. Boston also serves as county seat of Suffolk County. Wikipedia
Area: 259 km2 calculated
Seattle is a coastal seaport city and the seat of King County, in the U.S. state of Washington. With an estimated 652,405 residents as of 2013, Seattle is the largest city in the Pacific Northwest region of North America and the fastest-growing major city in the United States. Wikipedia