Cambridge ( KAYM-brij) is a city in Middlesex County, Massachusetts, United States. It is a suburb in the Greater Boston metropolitan area, located directly across the Charles River from Boston. The city's population as of the 2020 U.S. census was 118,403, making it the most populous city in the county, the fourth-largest in Massachusetts behind Boston, Worcester, and Springfield, and ninth-most populous in New England. The city was named in honor of the University of Cambridge in Cambridge, England, which was an important center of the Puritan theology that was embraced by the town's founders. Founded in December 1630 during the colonial era, Cambridge was one among the first cities established in the Thirteen Colonies, and it went on to play a historic role during the American Revolution. In May 1775, approximately 16,000 American patriots assembled in Cambridge Common to begin organizing a military retaliation against British troops following the Battles of Lexington and Concord. On July 2, 1775, two weeks after the Second Continental Congress in Philadelphia formally established the Continental Army and appointed George Washington commander of it, Washington arrived at Cambridge Common to take command of the Patriot soldiers camped there. Many of these soldiers played a role in supporting Washington's successful siege of Boston, which trapped garrisoned British troops from moving by land, forcing the British to ultimately abandon Boston. Cambridge Common is thus celebrated as the birthplace of the Continental Army. Harvard University, an Ivy League university founded in Cambridge in 1636, is the oldest institution of higher learning in the United States.