The Madrid Codices were discovered in Spain in 1965. The two manuscripts were found in Madrid’s Biblioteca Nacional de España after being miscatalogued and effectively lost among the library’s holdings.
Leonardo created Madrid Codex I mainly in the 1490s, focusing on mechanics, statics and machines. Madrid Codex II dates largely from 1503 to 1505 and includes material on fortifications, geometry, engineering and the Sforza monument. Together, the volumes contain hundreds of pages of notes and drawings and represent a major addition to the surviving record of Leonardo’s scientific work.
The manuscripts had reached Spain through Pompeo Leoni, a sculptor who worked at the court of Philip II. They later passed through royal and library collections, where a cataloguing error caused them to disappear from scholarly view for generations. Although the find dates to 1965, the discovery was publicly announced internationally in 1967—a timing detail that sometimes causes confusion.
The Madrid Codices are not a single book but two related Leonardo manuscripts, identified today as Madrid I and Madrid II.