This is a sub-project for the Colonial Americas Master Project.
New Spain, formally called the Viceroyalty of New Spain (Spanish: Virreinato de Nueva España), was a viceroyalty of the Spanish colonial empire, comprising primarily territories in what was known then as 'América Septentrional' or North America. Its capital was Mexico City, formerly Tenochtitlan, capital of the Aztec Empire. New Spain was established following the Spanish conquest of the Aztec Empire in 1521, and at its greatest extent included much of North America south of Canada: all of present-day Mexico and Central America (except Panama), most of the United States west of the Mississippi River and the Floridas.
New Spain also included the Spanish East Indies (Philippine Islands, Mariana Islands, the Caroline Islands, Taiwan, and parts of the Moluccas) and the Spanish West Indies (Cuba, Hispaniola with Haiti and the Dominican Republic, Puerto Rico, Jamaica, Cayman Islands, Trinidad, and the Bay Islands).
Administrative units included Las Californias (present-day Arizona, California, Nevada, Baja California, Baja California Sur, western Colorado, Utah and south Wyoming), Nueva Extremadura (including the present-day states of Coahuila and Texas), Santa Fe de Nuevo México (including parts of Texas and New Mexico)  and Louisiana (including the western Mississippi river basin and the Missouri River basin).
New Spain was the first of four viceroyalties created to govern Spain's foreign colonies. New Spain was ruled by a viceroy in Mexico City who governed the various territories of New Spain on behalf of the King of Spain. The Viceroyalty of Peru was created in 1542 following the Spanish conquest of the Inca Empire. In the 18th century the Viceroyalty of New Granada, and the Viceroyalty of the Rio de la Plata were also created.