The starting point of the Freedom Trail. The Boston Common is known to be one of the oldest public parks in the country. The park is almost 50 acres in size. Today, Boston Common is the anchor for the Emerald Necklace, a system of connected parks that winds through many of Boston's neighborhoods. The "Common" has been used for many different purposes throughout its long history. Until 1830, cattle grazed the Common, and until 1817, public hangings took place here. British troops camped on Boston Common prior to the Revolution and left from here to face colonial resistance at Lexington and Concord in April, 1775.