The Spanish conquest of Mexico transformed Aztec society, replacing the complex city-state system with colonial rule. Tenochtitlan fell to Hernán Cortés in 1521, ending the Aztec Empire and ushering in the Viceroyalty of New Spain. New Spain saw dramatic changes in governance, economy, and culture. A racial caste system emerged, with Spanish-born peninsulares at the top. The economy focused on exporting silver and raw materials, while Catholicism and Spanish language became dominant.