Winthrop is a city in Suffolk County, Massachusetts, United States. The population was 17,497 at the 2010 census and as of 2019 the population has grown to an estimated 18,544. Winthrop is an ocean-side suburban community in Greater Boston situated at the north entrance to Boston Harbor, close to Logan International Airport. It is located on a peninsula, 1.6 square miles (4.2 km²) in area, connected to Revere by a narrow isthmus and to East Boston by a bridge over the harbor inlet to the Belle Isle Marsh Reservation. Settled in 1630, Winthrop is one of the oldest communities in the United States. It is also one of the smallest and most densely populated municipalities in Massachusetts. It is one of the four cities that comprise Suffolk County. It is the southernmost part of the North Shore, with a 7-mile (11 km) shoreline that provides views of the Atlantic Ocean to the east and of the Boston skyline to the west.