MOSCOSO EXPEDITION. Luis de Moscoso Alvarado was a member of Hernando De Soto's expedition to explore La Florida-today's southeastern United States-and to obtain gold and other riches from the native peoples of the North American continent. The army of an estimated 600 men sighted land on May 25, 1539, on the western coast of Florida near what is now Tampa Bay, and landed on May 30. Over the next four years the expedition traveled throughout the southeastern United States. On May 21, 1542, De Soto died from a fever at the Mississippi River in what is now Arkansas; command of the expedition was transferred to Moscoso. The remainder of the journey is commonly known as the Moscoso expedition. The primary goal of its surviving members was to find an overland route back to New Spain (now Mexico). Many attempts have been made to reconstruct the route of the expedition, nearly all of which bring it into Texas in the summer of 1542.
Full article on the Texas State Historical Association's Handbook of Texas Online