A bibliographic mystery concerning Thomas Jefferson’s personal library has finally been solved. A number of his books have been found at Washington University in St. Louis, where they’ve been stored for the last 131 years.

Among the 74 volumes identified as Jefferson’s are architecture books he used to design the University. Two of them, by Fréart de Chambray and Andrea Palladio, are referenced in his designs for the pavilions and contain handwritten notes and calculations. Also discovered was his Greek edition of Aristotle’s Politica, said to be among the last books he read just before his death. And, found tucked in a volume of Plutarch’s Lives, a tiny scrap of paper with Greek notes in his hand (pictured).

“Our discovery provides an amazing and intimate look into Jefferson’s world,” says Leslie Green Bowman, president of Monticello and the Thomas Jefferson Foundation. “To find his handwritten notations is like peering over Jefferson’s shoulder to see his mind at work.”

“We thought these books had been lost to time, but now they’ve been found halfway across the country,” says UVA architectural historian Richard Guy Wilson. “We’re hopeful Jefferson’s notes will help illuminate how he adapted his architectural ideas so we can trace how his motifs developed over time.”

After his death, Jefferson’s personal library was auctioned off to settle debts on his estate, Monticello. The whereabouts of books sold during this 1829 auction, however, have puzzled scholars for years. Records do not survive of the buyers. One clue was a letter from Jefferson’s grandson-in-law, Joseph Coolidge, which mentioned titles he wished to purchase at the sale, but then the trail grew cold. If the Coolidge library was still extant, its whereabouts were unknown.

Then Monticello scholar Ann Lucas Birle (Col ’86, Arch ’89) stumbled on an 1880 article in the Harvard Register about a significant bequest of books of “rare and great value” to Washington University in St. Louis by Ellen and Edmund Dwight—the Coolidges’ daughter and son-in-law.

In February, Birle and fellow Monticello researcher Endrina Tay traveled to Washington University to examine the collection, and Tay was able to authenticate the books, which bore Jefferson’s distinctive ownership mark. It was the culmination of three months of intense and thrilling detective work, the scholars say.

Birle and Tay continue to work with their Washington University colleagues to reconstitute the 3,000 books that were in the 1880 bequest—and say they expect to discover more Jefferson and Jefferson family treasures among them.