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The Portland Observatory, built in 1807 at Portland, Maine, is the last surviving maritime signal...

The Portland Observatory, built in 1807 at Portland, Maine, is the last surviving maritime signal tower in the United States. Using both a telescope and lantern, two-way communication between ship and shore was possible several hours before an incoming vessel reached the docks. Portland has a deep harbor sheltered by numerous islands. Ships entering the harbor are not directly visible from the wharfs, which created problems for merchants trying to prepare for the arrival of cargoes. This problem was solved in 1807 when Captain Lemuel Moody organized the construction of an observatory on Portland's Munjoy Hill, visible from both the open ocean and the wharfs. During the War of 1812, the observatory was used as a watch tower. The 86-foot (26 m) tall observatory (7 stories) is octagonal and lighthouse-shaped, with a fieldstone base, and stands 222 feet (68 m) above sea level. The observatory's 'lantern' (cupola) included a P & J Dolland Achromatic Refracting Telescope, which could identify ships 30 miles (48 km) to sea. That telescope disappeared from the observatory in 1939. The observatory has been renovated numerous times over the years, including a Works Progress Administration