In 1457 the king of Portugal, Afonso V (1432-1481), commissioned the monastery of San Michele in Murano to make a world map. Fra Mauro (active ca. 1430-ca. 1459/1464) worked on the map for the next two years in collaboration with Andrea Bianco (active ca. 1430-ca. 1464) and some Venetian writers and artists. Account books show that the assigned task was to make a copy of a pre-existent world map and its accompanying texts. Afonso V’s copy of the world map, which unfortunately has been lost, was sent to Lisbon before April 24, 1459, under the care of a “messer Stefano Trevisan”, who may have been a patrician of the Republic of Venice.

The commissioning of the map took place in the context of important diplomatic, political, and commercial exchanges between Portugal and the Italian states. Beginning in 1455, Afonso V negotiated with pope Callixtus III (1378-1458) over his nation’s participation in the crusade for the re-conquest of Constantinople, and obtained papal bulls recognizing Portuguese primacy in the exploration and conquest of Africa. To incentivize trade, the king provided major fiscal advantages to Italian companies and turned to Italian sources to bring his nautical and cosmographic maps as up to date as possible.

In 1460, Portuguese ambassadors visited Florence, where they met humanist scientist Paolo dal Pozzo Toscanelli (1397-1482), who showed them a “large illustrated world map” in the possession of the Florentine knight and bibliophile Francesco Castellani (ca. 1417-1494).