The Portland Observatory is located at 138 Congress Street in the Munjoy Hill area of Portland Maine. It was built in 1807 and is the only remaining historic maritime signal station in the United States. It was designated a historic landmark in 2006 and is open to the public as a museum.
Portland has a deep harbor that is surrounded by many islands. The ships entering the harbor were not visible from the wharfs, which created problems for merchants preparing for the arrival of their cargos. Captain Lemuel Moody organized the construction of the observatory which could be seen from the ocean and the wharfs.
Using both a telescope and signal flags, two way communication between ship and shore was made possible several hours before an incoming ship reached the docks. The observatory is 7 stories high. During the War of 1812, it was used as a watch tower.