Duchy of Milan

State · 1402–1539 CE · at its largest around 1422 CE

A duchy in Lombardy created for the Visconti family in 1395 and later held by the Sforza, one of the major Italian states, which became a focus of French and Habsburg rivalry in the Italian Wars.

On its lands while it lasted

• Voynich manuscript (c. 1410 CE): An illustrated codex written in an unknown script that has never been deciphered, probably made in northern Italy; its vellum is radiocarbon-dated to the early 15th century. It is held by Yale’s Beinecke Library.
• The Last Supper (1495–1498 CE): Leonardo da Vinci's mural in the refectory of Santa Maria delle Grazie in Milan, depicting Jesus announcing that one of the apostles will betray him.

More on Wikipedia.