ssion. The emperor, however, had already commissioned Hernando de Soto on April 20,1537, to lead the expedition in conquest of Florida.
 On March 18, 1540 the emperor awarded Cabeza de Vaca the title of Adelantado (a title awarded to conquerors and discoverers) and a royal contract for the governorship of Rio de la Plata, a region in South America that stretches from Peru to the Straits of Magellan and includes modern- day Paraguay. Cabeza de Vaca accepted the commission and set sail for Rio de la Plata from Cadiz on December 2, 1540, with four ships and four hundred men. After a five-month sea journey, Cabeza de Vaca's expeditionary force landed at the island of Santa Catalina, Brazil on March 29, 1541. After an eight-month stay in Brazil, Cabeza de Vaca led the expedition on an overland one thousand mile march to Paraguay. Along the way, Cabeza de Vaca was the first European to see the Igauzu Falls. The expedition arrived in Asuncion on March 11, 1542, and Cabeza de Vaca took command of Rio de la Plata, replacing the interim governor Martinez de Irala.
 Cabeza de Vaca's term as adelantado of Rio de la Plata was marked by a series of progressive reforms for the treatment of natives and for handling conflict with other Spanish officials. Rolena Adorno and Patrick Pautz in their history of Cabeza de Vaca's life note that "the title of adelantado gave Cabeza de Vaca supreme powers as judicial and military ruler " in Rio de Plata, but the title "meant little to conquistadors and soldiers already established in the area who jealously guarded the prerogatives they had claimed for themselves" (Vol.1, 387-88). Most historians report that the colonists of Rio de la Plata and former governor Irala were at odds with Cabeza de Vaca over his reform policies towards the treatment of the natives. On April 8, 1544, Cabeza de Vaca returned to Asuncion from an unsuccessful expedition seeking the mythical city El Dorado and found himself faced with a revolt of the colonists led by Irala. Cabeza de Vaca was arrested on April 25, 1544, imprisoned for eleven months, and sent back to Spain for imprisonment on March 8, 1545.
 Cabeza de Vaca arrived in Seville on September 2, 1545, was imprisoned in Madrid for three months, and released on bond to live under house arrest. Cabeza de Vaca was accused of a number of criminal charges including the abuse of native populations in South America, the abandonment of members of his expedition, the prohibition of trade with the natives, and the confiscation of the property of members of his expedition without compensation. On March 18, 1551, he was found guilty of the charges and sentenced by the Council of the Indies. His sentence included the stripping of all titles, banishment from the Americas, and a five-year banishment from Spain to a penal colony in Onan (now Algeria). Cabeza de Vaca appealed his conviction and his banishment from Spain was suspended, while his banishment from the Americas only included the Rio de la Plata region. Cabeza de Vaca eventually vindicated himself against the charges of professional incompetence in Rio de la Plata and restored his honor in the eyes of the royal court. He published a second edition of La Relacion in 1555, which included a second part detailing his account of his time as governor of Rio de la Plata.
 Cabeza de Vaca spent the remainder of his life in Seville. He was named by the emperor as Chief Justice of the Tribunal of Seville in 1556. His activities in his final years are largely unknown. The exact date of his death has never been determined, but recent historical research indicates that he died between 1559 and 1560 and is buried in the family vault in Jerez de la Frontera.
- Adorno, Rolena, and Patrick Charles Pautz. Alvar Nunez Cabeza de Vaca: His Account, His Life, and the Exploration of Panfilo de Narvaez. 3 vols. Lincoln: U of Nebraska P, 1999. (Paperback edition of the text and introduction 2003.)
- This work is the result of a project by the two authors since 1991. The massive three-volume set is a detailed analysis of the life, times, and writt