U.S. Coast and Geodetic Survey assistant Edwin Smith of Rockville, Maryland, oversaw construction and operations at the Gaithersburg Observatory. Original plans for the Ukiah and Gaithersburg observatories, prepared by the Central Bureau in Germany, called for iron buildings, but when replicas of the Japanese and Italian stations could not be built within the projected budget, Smith revised the plans to use wood instead. Construction of the Gaithersburg Latitude Observatory was completed in August 1899, it received its Zenith Telescope in September of that year, and the facility officially opened on October 18, 1899. The observatory was built with a double wall of Georgia and Virginia pine to reduce temperature differences that might affect the heat-sensitive Zenith Telescope, and its roof was designed in two parts that moved east and west on iron wheels operated manually by a rope pulley system. Its six-foot, six-inch full opening was always used to accommodate the large Zenith Telescope, which pointed at the zenith directly above a location and used extremely sensitive spirit bubble levels for the angle measurements needed to determine astronomic latitude. The motion-sensitive telescope was mounted on a pier sunk into the ground to prevent vibrations from traffic or trains from affecting observations. Though small and devoted to specialized work, the observatory had international importance: its research provided all the data used in polar motion studies for decades and fostered international cooperation during periods of war and international strain. From its construction in 1899 until human observers became obsolete and it closed in 1982, the Gaithersburg Latitude Observatory played an integral role in the study of Earth's scientific behavior. After closing, it stood unused and deteriorated, but the City of Gaithersburg adopted historic preservation policies, designated the observatory as its first officially designated historic site, received it from the National Oceanographic and Atmospheric Administration for historic monument purposes in May 1987, and granted an easement to the Maryland Historical Trust. Restoration funds were secured, and on December 20, 1989, the observatory was designated a National Historic Landmark. The Gaithersburg International Latitude Observatory, its Meridian Mark Pier, and five monuments are listed on the National Register of Historic Places.