Juan Díaz de Solís (ca. 1470-1516), the pilot major of Castile, sailed under the Spanish flag to explore the Americas, where he discovered the Río de la Plata.
Juan Díaz de Solis was evidently born in Portugal, although his ancestry was Spanish. As a young man, he visited India perhaps several times as a seaman in Portuguese service. Dissatisfied with his meager and often unpaid wages, he served for a time with French corsairs. When he and his French associates captured a Portuguese caravel returning from the Gold Coast, this made his return to Portugal impossible, so he transferred his services to Spain. He had by this time become a skilled pilot.
Solís was in Spain by 1508, and in that year he embarked on a discovery voyage with Christopher Columbus's former companion Vicente Yáñez Pinzón. Their exact route is a matter of dispute, but they attempted to find the much-sought strait to the Spice Islands and spent part of their time exploring the coast of Veragua (Nicaragua).
Upon returning to Spain in 1509, Solís was imprisoned because he and Pinzón had quarreled; the authorities at this point favored the older navigator. A more careful review of the matter soon followed, and Solís was released. He now enjoyed the esteem of King Ferdinand V, and when Amerigo Vespucci, the first pilot major of Castile, died in February 1512, Solís became his successor.
As pilot major, Solís embarked in 1515 on his last voyage, the purpose of which was to find a passage into the Pacific Ocean. Once in the Pacific, he was to proceed to the Far East if possible. The three caravels allotted him were small so that they could explore shallow coastal waters that vessels of greater draft could not penetrate. The Portuguese knew the purpose of Solís's voyage and, fearing to lose their monopoly on the Oriental trade, attempted unsuccessfully to sabotage the undertaking before Solís left Sanlúcar de Barrameda on Oct. 8, 1515.
After carefully working its way down the Brazilian coast, Solís's expedition entered the Río de la Plata. He explored the Uruguayan coast as far as Martin Garcia Island, and near here he went ashore with a party, including his two principal officers, Pedro de Alarcón and Francisco Marquina. Suddenly a band of Indians, presumably Charrúa, burst upon them and killed the landing group in plain view of those on shipboard. The leaderless expedition returned as quickly as possible to Spain and arrived there on Sept. 4, 1516.
Major accounts of Solís are in Spanish. In English, some information on him is in Pietro Martire d'Anghiera, De orbe novo (trans., 2 vols., 1912). The Solís discoveries receive attention in Germán Arciniegas, Amerigo and the New World (trans. 1955); and the voyages are placed in historical perspective in Charles E. Nowell, ed., Magellan's Voyage around the World (1962). □