Born around the year 100 CE and active in Alexandria, Egypt during the 2nd century, Claudius Ptolemy was a scholar and author who wrote several important scientific treatises, including the Almagest, the Geography, and the Tetrabiblos. The Geography, also titled variously the Geographia or Cosmographia, contains information on the geography of the ancient Roman world, including a gazetteer and a cartographic manual.

The work was influential in the Islamic world during the Middle Ages and was translated from the original Greek and republished numerous times in Europe during the late Medieval and Renaissance periods. Between the 15th and 17th centuries, upwards of 40 editions of Ptolemy’s Geographia were published in cities across Europe. Most editions are in Latin, Greek, or both, with some later editions appearing in Italian and French.

While it is unknown whether Ptolemy’s original edition contained maps, medieval and modern European editions almost invariably did. Ptolemy's coordinates were used by various later cartographers to construct maps, which were then frequently attributed to Ptolemy himself. The standard roster of 26 regional maps – 10 European, 4 African, and 12 Asian – was frequently supplemented by a composite world map. Many editions, particularly those published after European explorations in the Americas, include updated world maps and maps of additional areas of the world not represented in Ptolemy’s original work. These maps are frequently identified by title as tabula nova (“new chart”) or tabula moderna (“modern chart”).

The Library of Congress holds copies of editions of the Geographia in both the Geography and Map Division and the Rare Book and Special Collections Division. Many of the copies in the Geography and Map Division were collected by Philip Lee Phillips, the first Chief of the Map Division, who held that position from 1897 to 1924. The majority of the copies in the Rare Book and Special Collections Division are part of one of two collections: the Thacher Collection, which was donated by John Boyd Thacher and his widow in the 1910s and 1920s; and the Rosenwald Collection, which was donated by Lessing J. Rosenwald in the mid-20th century. Items must be requested in the reading room in which they are held. Additionally, a few more recent editions, as well as numerous scholarly works about the Geographia, Ptolemy, and his world, are held in the Library’s general collections.

This guide contains a list of all editions of the Geographia held in the Library of Congress, with notes on contributors, date and place of publication, the language of the text, and the reading room(s) which hold copies. The Digital Collections Gallery displays digitized copies of Ptolemaic atlases which can be viewed on the Library’s website. Selected reference sources, both print and online, are also described in the next two sections. Finally, the guide suggests search strategies for researching pre-modern and early modern materials. Researchers with additional questions are encouraged to contact reading room staff through Ask a Librarian.