CHACÓN (Ciaconius), ALONSO. - Born in Baeza (Granada) in 1540, died in Rome on 15 February 1599. He entered the Order of Preachers, served as prior of the convent of S. Tommaso in Seville; upon coming to Rome during the pontificate of Gregory XIII (1572–85), he became penitentiary at S. Maria Maggiore. He lived in Rome on the Pincian Hill, where he established a library and a museum noted by Macarius (Hagioglypta; Paris 1856, p. 2). He was among the explorers of the reopened subterranean cemeteries (of the Giordani) in 1578 and had copies made of the paintings, sarcophagi, and inscriptions, though some proved unsatisfactory (J. Wilpert, Die Katakombengemälde und ihre alten Copien, Freiburg in Br. 1917), as were others from the cemeteries of Priscilla, S. Valentine, Domitilla, and the underground of S. Nicola in Carcere; these copies are preserved in Cod. Vat. Lat. 5409.
From an examination of his correspondence in the Chigi Library, Mabillon recognized that Chacón had planned two works: one on Roman antiquities and another, Bibliotheca a plurimis antea auctoribus dispersim instituta et collecta, deinde ab aliquot in epitomen redacta (J. Mabillon, Museum Italicum, I: Iter Italicum litterarum, Paris 1724, p. 96). Only the first volume, up to the letter E, was printed in Paris; the manuscript was rediscovered by G. B. De Rossi in 1831 (Bull. di arch. crist., 1st ser., 2 [1864], p. 88). His most famous work, however, was published posthumously: Vitae et res gestae Summorum Pontificum a Christo Domino usque ad Clementem VIII nec non S. R. E. Cardinalium, by Alfonso Chacón of Baeza, of the Order of Preachers and Apostolic Penitentiary, published in Rome in 1601 under the care of his nephew Alfonso Ciacconio. Though surpassed in many respects, it remains indispensable for consultation. Later continuations were provided by F. Cabrera Morales, A. Vittorelli, F. Ughelli, G. Allandro, L. Wadding, C. Beccillo; A. Oldoini extended it in 1677 to Clement IX, and M. Guarnacci in 1751 to Clement XII.