The Portsmouth Harbor lighthouse is located on the grounds of Ft. Constitution in New Castle, New Hampshire.  The first lighthouse was built in 1771 at Fort William.  A second, taller tower was erected in 1804 with a cast iron tower erected in 1878 inside of the 1804 tower, which was eventually dismantled.  The The grounds of Ft. Constitution are open during the day; tours of the lighthouse during periodic open houses held by the Friends of Portsmouth Harbor Lighthouse.