Born in Milan on October 10, 1815, Girolamo d'Adda came from an ancient noble family that traces its origins back to 700 AD.

[1] In 1848, during the Five Days of Milan, with Carlo Tenca and Cesare Cantù he co-authored a document 'Saluto ai fratelli genovesi' (Greeting to the brothers from Genoa) where they addressed small regions of Italy, calling for unification.

In that period he grew close to monarchists-unitarians and their leader Cristina Trivulzio Belgiojoso, however, in 1853 he pleaded loyalty to the Emperor after a failed attempt on the life of Franz Joseph I of Austria.

[2] An anti-industrialist, bound to a static conception of the relations between the various strata of society, and confronted with a world that he increasingly criticised for its materialism and atheism, Girolamo d'Adda wrote a foreword for a biography of Benjamin Franklin in which he summarised all these doubts, praising how one of the most famous men in the United States, even as a philosopher, had never disavowed his religious spirit and, even as a republican, had never forgotten to exercise a certain moderation in defining his positions.

[4][5] An important achievement as a collector was the discovery and 1866 presentation of a letter, written by Christopher Columbus to Luis de Santangel in 1493.