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The James Melville Gilliss Library

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The  James Melville Gilliss Library, located on the grounds of the United States Naval Observatory, is one of the preeminent astronomical libraries in the United States. The library includes over 90,000 books, including a substantial 19th century scientific journal collection. Also of note is the 800 volume rare book collection featuring many of the most important scientific works dating from 1482 to 1800, and the substantial manuscript collection of observation journals and correspondence from the 19th century Transit of Venus expeditions to decades of observing by USNO scientific staff. 

In 1843, while visiting Europe to inspect the progress on instruments being built for the USNO's first "permanent" site in Foggy Bottom, LT James Melville Gilliss (at right) toured a number of European observatories and purchased many books deemed essential to a new observatory's operation.  This modest collection of a few hundred volumes, which cost somewhere around $800, formed the nucleus of the Library's now-extensive catalog.  After a major renovation in 1996, the Library was dedicated to Gilliss upon its re-opening that year.

The library collections are searchable via Urania, the online catalog, accessible here.

Latest USNO Publications: 

Information on the latest issues of the Air Almanac, Astronomical Almanac, Nautical Almanac, and Astronomical Phenomena are available on the Astronomical Applications website.  

The 2024 edition of the Air Almanac, in PDF format, may be found here.

Note:  The annual Astronomical Phenomena booklet is generally made available in PDF at around the beginning of the calendar year.  Since it contains material protected under British Crown copyright you must use the link below to His Majesty's Nautical Almanac Office to obtain a copy.  You may also order a hardcopy from the U.S. Government Printing Office here.
Astronomical Phenomena [present year and limited archive]

Reference Assistance:

The USNO Library provides limited telephone, in-person, and email reference assistance. We are open to outside researchers by appointment only. Please call (202) 762-1463 or email to make an appointment. Please take a look at our online catalog prior to making your appointment and have the author, title, and call number ready if possible. 


Personnel stationed on or employed by USNO are permitted to check out books. The Library participates in interlibrary loan. Rare, Special Collection, Archival material, and Reference books, as well as bound periodicals, do not circulate. The Library reserves the right to refuse to circulate or permit the reproduction of any items considered unique or fragile. Items over 100 years old are not available for interlibrary loan.
Have a question regarding the USNO Library collection? Would you like to volunteer or intern with the USNO Library? Ask the USNO Librarian! Email the library at

Library History

There is a lot of history in the Library; over the years it has served as not just a library, but also as a social and ceremonial center of the Observatory.  To learn more about the Library's history, you can take a look at the library's dedication ceremony or learn the story behind the seal of the Observatory, which is also used for the Library's bookplate. 



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