The original National Observatory was authorized by President Tyler in 1842 and completed in 1844 according to plans prepared by Lieutenant James Melville Gilliss. The observatory was the site of notable advances in astronomy and mathematics, and is associated with its first superintendent, Matthew Fontaine Maury, who supervised the publication of numerous volumes of oceanographical charts, and was the author of the first oceanographical textbook. The observatory installed a new transit circle instrument by the end of the Civil War. The domed south wing housed the 26-inch Great Equatorial telescope, the largest of its day, installed in 1873. In 1877, astronomer Asaph Hall discovered the moons of Mars with this instrument.
From its inception, the observatory was authorized to calculate and keep official time, which was indicated by the dropping of a time ball from the flagstaff each day at noon. By 1878, poor atmospheric conditions in Foggy Bottom led Congress to authorize relocation to a new site, and in 1893, the observatory moved to its new home on Massachusetts Avenue. After its relocation, the property was transferred to the Navy’s Bureau of Medicine and Surgery to serve as a Museum of Hygiene, and later the Naval Medical School.
DC Inventory: November 8, 1964 (Joint Committee on Landmarks)
National Register: October 15, 1966
National Historic Landmark: January 12, 1965