The Trivulzio family, listed among the Milanese patriciate in 1277, played a prominent role in the political and military affairs of the Duchy of Milan, with its members from the early 15th century bound to the duke by a strong feudal homage.

One of the most illustrious and celebrated figures is undoubtedly Gian Giacomo, known as Il Magno (1442–1518), who was educated in arms and letters at the ducal court of Francesco Sforza, and later that of his son Galeazzo Maria. He was at the center of many undertakings: in 1477, he was appointed to the regency council of the duchy; in 1480, he purchased the lordship of Mesolcina from Enrico de Sacco, which elevated him politically and economically as an intermediary between the Duke of Milan and the Rhaetian Leagues. He served King Ferdinand I of Naples and Pope Innocent VIII. In 1487, he married Beatrice de Avalos, having previously been widowed by his first wife, Margherita Colleoni. In 1495, he switched allegiance to France, becoming an advisor to the king, chamberlain, and commander of King Louis XII's army when it entered Milan in 1499. He was later made Marquis of Vigevano and Melzo, Marshal of France, and Lieutenant of Milan. He was also a patron of the arts and literature, commissioning the famous series of tapestries known as the Months, designed by Bartolomeo Suardi (Bramantino) and woven in Vigevano, now held in the Civic Museums of the Sforza Castle.

In the 17th century, the family was led by Gian Giacomo Teodoro Trivulzio (1597–1656), who served Philip III of Spain and was the imperial commissioner for Ferdinand II of Austria. For his services, he was granted the title of Prince, the treatment of Illustrious of Spain, and the citizenship of the Empire. After the death of his wife Giovanna Grimaldi in 1620, Gian Giacomo Teodoro embraced ecclesiastical life and was made Cardinal in 1629. In 1638, he was appointed General Governor of the Duchy’s military and Superintendent of Fortresses in 1639, later becoming Governor of Arms, Viceroy, and Captain General of the Kingdom of Aragon in 1642. During the Sicilian Revolts in 1647, he was appointed president of the kingdom and captain general, later becoming Viceroy of Sardinia in 1649. In 1655, he was made Governor and Captain General of the Duchy of Milan, the only one from his hometown to receive this title. He was also a patron of the arts, enhancing the residences of Melzo and Codogno and building an important collection of paintings. His career was eclipsed by that of his grandson, Antonio Teodoro Trivulzio, who died at the age of 29 without heirs, forcing him to leave his fortune and surname to his cousin Gaetano, son of his guardians, Ottavia Trivulzio and her husband Tolomeo Gallio, Duke of Alvito. Antonio Tolomeo Gallio Trivulzio, son of Antonio Teodoro Gaetano and Maria Borromeo, is remembered in Milan for donating his entire fortune and palace to establish the Pio Albergo for the care and assistance of the poor (1771).

The family continued through the branch of the Marquises of Sesto Ulteriano, whose history is closely linked to that of the Trivulzio Museum and the Trivulziana Library. The collection has ancient origins, dating back at least to the second half of the 15th century. Key figures in expanding the collection were brothers Alessandro Teodoro (1694–1763) and Carlo Trivulzio (1715–1789) in the mid-18th century. The history of the collection continued with Gian Giacomo IV Trivulzio (1774–1831), who greatly expanded the family's holdings through a meticulous purchasing campaign. His heirs were his children Giorgio Teodoro (1803–1856), who married Marianna Rinuccini in 1831, and Rosina Trivulzio (1800–1859), wife of Giuseppe Poldi Pezzoli and mother of Gian Giacomo, who shared her grandfather's passion for collecting and bequeathed her possessions to establish the Poldi Pezzoli Museum House.

Giorgio Teodoro's successor was his son Gian Giacomo (1839–1902), who served as a senator of the Kingdom from 1896 and expanded the Dante and Petrarchian collections. In 1864, he married Giulia Amalia Barbiano di Belgiojoso, bringing with her a dowry of 634 ancient and valuable manuscripts. Gian Giacomo was the first to open the library to scholars. He appointed his cousin Giulio Porro as librarian, who authored the first catalog of the collection, later succeeded by Carlo Ermes Visconti and Emilio Motta. In 1935, the art collection was transferred to the Civic Art Collections of the Municipality of Milan, while the Trivulziana Library was annexed to the Civic Historical Archive.

Bibliography
F. CALVI, Storia e genealogia delle famiglie Barbiano e Belgiojoso, in Famiglie notabili milanesi. Cenni storici e genealogici raccolti da F. BAGATTI-VALSECCHI, F. CALVI, L.A. CASATI, D. MUONI, L. PULLÉ, Milan 1875.
D.E. ZANETTI, La demografia del patriziato milanese nei secoli XVII, XVIII, XIX, Pavia 1972.
ALESSANDRA SQUIZZATO, Ricerche storico-artistiche in Trivulziana fra Otto e Novecento. Il contributo e la regia di Emilio Motta, in Annali di Critica d’arte, XII (2016), pp. 435-450.

Documentary Fund

The Trivulzio Archive consists of four series: Codici Trivulzio, Biblioteca Trivulzio, Miscellanea Trivulzio, and Carteggio Trivulzio. It has been preserved since 1958 at Villa Belgiojoso in Merate, owned by Marianna Trivulzio Brivio Sforza, and is now housed at the Brivio Sforza Foundation. In 2014, the collection underwent a process of reorganization, cataloging, and partial preservation.
The Codici Trivulzio series consists of seventeen manuscripts and printed books, on parchment and paper, relating to the Trivulzio family. Fifteen of these belonged to the Trivulziana Library and were described by Giulio Porro in his Catalogo dei codici manoscritti della Biblioteca Trivulziana (1884).
The Biblioteca Trivulzio and Miscellanea Trivulzio series contain original documents, notes, and transcriptions by Emilio Motta, who was the curator of the Trivulziana Library from 1885 to 1920. Motta was also a historian and bibliographer, founder of the Bollettino storico della Svizzera Italiana in 1879, and a prominent member of the Lombard Historical Society and Comense Historical Society.
The Carteggio Trivulzio series holds letters written by or addressed to members of the Trivulzio family, collected and preserved by Marianna Trivulzio Brivio Sforza.