Georgetown Observatory (1841) The tour now moves south towards the Potomac River and passes the Georgetown Observatory. Georgetown is one only a handful of urban universities with its own working observatory, and Georgetown's was the first such building constructed in Washington. The work of the observatory confirmed the exact longitude and latitude of the Nation's Capital, a measurement so exact it is used by scientists to this day. At its peak, Georgetown's graduate studies program in astronomy was the largest in the country, but the "light pollution" of major cities and the construction of larger telescopes in remote locations diminished the program's reach. In 1971, the department was closed, but the building was spared following its being named a National Historic Landmark in 1973. Today's Georgetown Astronomy Club maintains the grounds and continues the tradition begin over 160 years ago. (Click on the photo to continue.)