The period during which Vespucci made his voyages falls between 1497 and 1504. Two series of documents on his voyages are extant. The first series consists of a letter in the name of Vespucci dated from Lisbon, Portugal, September 4, 1504, written in Italian, perhaps to the gonfalonier (magistrate of a medieval Italian republic) Piero Soderini, and printed in Florence in 1505; and of two Latin versions of this letter, printed under the titles of “Quattuor Americi navigationes” and “Mundus Novus,” or “Epistola Alberici de Novo Mundo.” The second series consists of three private letters addressed to the Medici. In the first series of documents, four voyages by Vespucci are mentioned; in the second, only two. Until the 1930s the documents of the first series were considered from the point of view of the order of the four voyages. According to a theory of Alberto Magnaghi, on the contrary, these documents are to be regarded as the result of skillful manipulations, and the sole authentic papers would be the private letters, so that the verified voyages would be reduced to two. The question is fundamental for the evaluation of Vespucci’s work and has given rise to fierce controversy; attempts to reconcile the two series of documents cannot generally be considered successful.
The voyage completed by Vespucci between May 1499 and June 1500 as navigator of an expedition of four ships sent from Spain under the command of Alonso de Ojeda is certainly authentic. (This is the second expedition of the traditional series.) Since Vespucci took part as navigator, he certainly cannot have been inexperienced; but it does not seem possible that he had made a previous voyage (1497–98) in this area (i.e., around the Gulf of Mexico and the Atlantic coast from Florida to Chesapeake Bay), though this matter remains unresolved.
In the voyage of 1499–1500 Vespucci would seem to have left Ojeda after reaching the coast of what is now Guyana. Turning south, he is believed to have discovered the mouth of the Amazon River and to have gone as far as Cape St. Augustine (latitude about 6° S). On the way back he reached Trinidad, sighted the mouth of the Orinoco River, and then made for Haiti. Vespucci thought he had sailed along the coast of the extreme easterly peninsula of Asia, where Ptolemy, the geographer, believed the market of Cattigara to be; so he looked for the tip of this peninsula, calling it Cape Cattigara. He supposed that the ships, once past this point, emerged into the seas of southern Asia. As soon as he was back in Spain, he equipped a fresh expedition with the aim of reaching the Indian Ocean, the Gulf of the Ganges (modern Bay of Bengal), and the island of Taprobane or Ceylon (now Sri Lanka). But the Spanish government did not welcome his proposals, and at the end of 1500 Vespucci went into the service of Portugal.
Under Portuguese auspices Vespucci completed a second expedition, which set off from Lisbon on May 13, 1501. After a halt at the Cape Verde Islands, the expedition traveled southwestward and reached the coast of Brazil toward Cape St. Augustine. The remainder of the voyage is disputed, but Vespucci claimed to have continued southward, and he may have sighted (January 1502) Guanabara Bay (Rio de Janeiro’s bay) and sailed as far as the Río de la Plata, making Vespucci the first European to discover that estuary (Juan Díaz de Solís arrived there in 1516). The ships may have journeyed still farther south, along the coast of Patagonia (in present-day southern Argentina). The return route is unknown. Vespucci’s ships anchored at Lisbon on July 22, 1502.