Editing United States Naval Observatory (section)

===Nautical Almanac Office===
In 1849, the Nautical Almanac Office (NAO) was established in [[Cambridge, Massachusetts]] as a separate organization. In 1866, it was moved to [[Washington, D.C.]], operating near Fort Myer. It relocated to the U.S. Naval Observatory grounds in 1893.<ref name="sky_and_ocean"/>

On 20&nbsp;September 1894, the NAO became a "branch" of USNO; however, it remained autonomous for several years.<ref name="sky_and_ocean"/>

The site houses the largest astronomy library in the United States (and the largest astrophysical periodicals collection in the world).<ref>{{cite web |publisher=Naval Meteorology and Oceanography Command |title=The James Melville Gilliss Library |series=Naval Oceanography Portal |website=usno.navy.mil |url=http://www.usno.navy.mil/USNO/library |access-date=2011-07-27 |archive-date=2011-07-26 |archive-url=https://web.archive.org/web/20110726020826/http://www.usno.navy.mil/USNO/library |url-status=dead }}</ref> The library includes a large collection of rare physics and astronomy books from the past millennium.