Conquistador is the Spanish word for “conqueror.” The Spaniards who arrived in North and South America in the late 1400s and early 1500s were just that—conquerors of the American Indians and their lands. In many cases, the Spaniards were the first Europeans to arrive in these lands, where they encountered native inhabitants including the Aztec of Mexico, the Maya of southern Mexico and Central America, and the Inca of western South America. By the mid-1500s these native peoples had been conquered, their populations decimated by the Spanish conquistadors. The conquest happened in two ways: First, the Spaniards rode on horseback and carried guns, while their native opponents were on foot and carried crude weapons such as spears and knives; and second, the European adventurers brought illnesses (such as smallpox and measles) to which the native populations of the Americas had no immunities, causing the people to become sick and die.

By 1535 conquistadors such as Francisco Pizarro (c. 1475–1541), Hernán Cortés (1485–1547), and Vasco Núñez de Balboa (1475–1519) had claimed the southwestern United States, Mexico, Central America, and much of the West Indies (islands of the Caribbean) for Spain.