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The James Melville Gilliss Library

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. 

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

Latest USNO Publications: 

Air Almanac 2021

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.


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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 Collections

Recently Cataloged Books, Electronic Journals, and Publications of the USNO and its staff 


Historical Photos, Artwork, and Objects

A sampling of the historical photos, artwork and objects contained within the library.


Library History

Learn more about the history of the library


Additional Resources

Links to additional online resources