The National Braidense Library was originated when the State Congregation for Lombardy, an organisation promoting the interests of the local community, acquired the library of Count Carlo Pertusati, and donated it to the Archduke Ferdinand, son of the Empress Maria Theresa of Austria, later governor of Lombardy.
In 1770, Maria Theresa, considering that Milan needed "an open library for the common use of anyone who wants to cultivate his mind, and acquire new knowledge", and that the Ambrosian library was not sufficient, because it was "rich in manuscripts", but not in "printed books", decided to assign the library of Pertusati to the public use.
Thanks to the dissolution of the Society of Jesus, decided in 1773 by pope Clemente 14th, the State acquired the Palace of the Collegio Gesuitico di Brera, built in the area of the 13th century convent of the Umiliati, and destined it to the library.
The library was opened to the public in 1786.
With the dissolution of the Society of Jesus, the State acquired also the book collections of the Collegio Braidense and of the Jesuit houses of San Fedele and San Girolamo, joining them to the Pertusati collection to constitute the initial nucleus of the library.
In 1778 there was the addition of the collection of the Bernese physician Albrecht von Haller, with precious scientific texts, then the collections of cardinal Angelo Maria Durini and colonel Baschiera, and a small part of the library of count Firmian.
The suppression of religious congregations, stated by the Emperor Joseph II, determined the acquisition of part of the ancient cloister libraries, and later also copies of books from the Imperial Library in Vienna.
During the Napoleonic age the library of the Collegio dei Giureconsulti was acquired, and the Scaccerni collection was donated by Francesco Melzi.
The growth of the collections was increased by the Avviso della Regia Intendenza Politica di Milano in April 1788, establishing the obligation to send to the library all the works published in the Milanese State. In 1793 also edicts and notices published by governmental authorities were included. In 1848 this statement was transformed in the act on legal deposit.
The Braidense, that already in the 1880 was appointed with the name of "Nazionale", looked like a great library of general character: its holdings spaced from the illuminated chorales coming from the Certosa of Pavia to the scientific books of the Haller collection, from the historical and literary works of the Durini legacy, famous above all for the editions of Latin and Greek classics of the 16th Century, to the theological works, the legal ones and the great general reference books.
During the 19th Century other collections further enriched the patrimony of the Braidense: the volumes donated by Hermes Visconti, the collection of the Numismatic Cabinet, the Bodonian collection Mortara, the Lattes collection of works of Jewish culture, the collection Carl Morbio, the miscellanea Viesseux and the library of Cesare Correnti.
In 1889 the theatre collection Corniani Algarotti was acquired, followed by the bequest De Capitani D'Arzago.
The collection of Alessandro Manzoni was donated in 1885.
Among the collections acquired in the 1900's it is worth mentioning the Novati library, the liturgical library of the Duchi di Parma, the chess collection, the Castiglioni collection and the photographic collection Emilio Sommariva.
The Institute has been carrying on since its foundation the twofold function of library of conservation, destined to a public of scholars of the historical and literary research and of mirror of the great Milanese library production, devoted to a larger range of users.