The John Winthrop Jr. Iron Furnace Site is a historic archaeological site at 61 Crescent Street, Quincy, Massachusetts. The site is called Braintree Furnace in some texts; the West Quincy location at the time of operation was in a part of Braintree, Massachusetts, that later became Quincy. Its importance lies in the fact that it was the first iron blast furnace established in what would become the United States. Furnace Brook, a stream which begins on the eastern slopes of the Blue Hills and meanders for about four miles from southwest to northeast through the middle of Quincy toward Quincy Bay, was named for the works site.