This palace was the residence of counts d'Arco until 1973, when last descendant Giovanna d'Arco stipulated that it become a public museum.
The local imperial palace was likely here during XII century. The remains of a two-meters thick wall seem to support this theory.
Duke Vincenzo I sold the building to his secretary and minister Annibale Chieppio, who enlarged it after buying a piece of land from the near Franciscans. 
When Giuseppe Maria Chieppio died in 1729, his son Scipione had the obligations, in case he had no children, to leave everything to his sister Teresa's first-born son. He died without children in 1740, and the family of Francesco Alberto d’Arco and Teresa Chieppio entered present Palazzo d’Arco. 
You can still see the Roman Holy Empire double-headed eagle with d'Arco's and Chieppo's coats of arms on the façade tympanum.

Present palace is an elegant neoclassical building by architect Antonio Colonna (1782-1792). Inside, you can still admire:
- the original furniture;
- paintings by Niccolò da Verona, Luini, Magnasco, Pourbus, Van Dyck and Giuseppe Bazzani;
- the library, rich of ancient books;
- the kitchen and its large collection of copperware;
- Salone dello Zodiaco (id est the zodiac hall), frescoed by Giovanni Maria Falconetto in 1520;
- the nice garden and its exedra.