The United States Naval Observatory is a building situated at 3450 Massachusetts Avenue NW in Washington, D.C.. It serves two main functions: astronomy and chronometry services for the Department of Defense and civilians; and the residence of the Vice President of the United States.

The United States Navy initiated the Depot of Charts and Instruments organization in 1830. Its main mission was to standardize timekeeping on ships by precisely measuring celestial phenomenon. The Depot was reorganized in 1844 and became the US Naval Observatory, housed in a building located near where the Lincoln Memorial is now. The Naval Observatory became a valuable astronomy resource, to the point where they started issuing astronomical almanacs in 1855. (Asaph Hall, a Naval Observatory astronomer, discovered Deimos and Phobos in 1877.)

The Naval Observatory gained one of its most well-known features in 1845. After developing standards for keeping time, the Observatory deployed a method for coordinating time between clocks. At the peak of the Observatory's dome, a 9.6-inch ball was installed on a mast. Precisely at noon each day, the ball would descend -- and ships in the nearby Potomac River could set their timepieces (in addition to the residents of Washington). With the advent of the telegraph, the Observatory transmitted accurate times across the country. Nowadays, the USNO hosts an atomic clock which keeps the standard time for the entire country, known as the Master Clock. This steadily accurate time signal is used by the military for the Global Positioning System, scientists conducting experiments, and even citizens via telephone, radio, and Internet.

After realizing that low-lying swampland was not the best location for an observatory (the neighborhood housing the USNO was and still is known as "Foggy Bottom"), it was moved in 1893 to higher ground, in the hills above Georgetown. At the time, this was far outside the city center. This location is now nestled among rows of foreign embassies. When this site was constructed, a separate building North of the main complex was built with the intention of being the USNO Superintendent's residence. This house turned into the home of the Chief of Naval Operations in 1929 and was re-allocated to the Vice President in 1974.

Today the USNO continues to perform research and experiments with astronomy and time using both its main campus in Washington and peripheral sites in Colorado, Arizona, West Virginia, Chile, New Zealand, and elsewhere -- including outer space (although the Vice President doesn't live there).

You can even go there yourself! That's right, with proper scheduling (and notification) you can register on the USNO website to take a tour and look through a telescope. Of course, this is only after the US government takes a telescope to your life history to determine whether or not you are a risk to national security. For more information, see http://www.usno.navy.mil (or ask momomom since she reminded me of this!).