in addition to the other islands of the central group, graciosa was explored by portuguese navigators during the first quarter of the 15th century. although there exists no accounts of the first sighting of the island. may 2, 1450 has frequently been referred to as the date of the islands "discovery", although there exists no documentation to support this date. paradoxically, it is clear that in 1440, by order of prince henry the navigator, cattle and swine were settled on the island in order to facilitate colonization.