Boston is the capital city and most populous city of the Commonwealth of Massachusetts, a state in the United States. The largest city in New England, it is considered the unofficial capital of the New England region. The city-proper had an estimated population of 596,638 in 2005, and lies at the center of America's eleventh-largest metropolitan area, Greater Boston, which is home to 4.4 million people. Founded in 1630, Boston was the location of several major events during the American Revolution, including the Boston Massacre and the Boston Tea Party. With many colleges and universities within the city and surrounding area, Boston is a center of higher education and a center for health care. The city's economy is also based on research, finance, and technology — principally biotechnology. Boston is struggling with gentrification issues, and has one of the highest costs of living in the United States.