Following the voyages of Christopher Columbus, Spain rapidly emerged as the dominant European power in the Americas during the sixteenth century. Motivated by the pursuit of wealth, territorial expansion, religious influence, and imperial prestige, Spanish explorers, conquistadors, missionaries, and settlers established colonies throughout the Caribbean, Central America, South America, and parts of North America.

Spanish expansion accelerated after reports of enormous wealth reached Europe from newly encountered territories. Conquistadors such as Hernán Cortés and Francisco Pizarro led military campaigns that overthrew the powerful Aztec and Inca Empires, bringing vast amounts of gold and silver under Spanish control. These conquests dramatically increased Spain's wealth and strengthened its position as one of the most powerful empires in Europe.

The extraction of precious metals from the Americas transformed the global economy. Massive shipments of gold and silver crossed the Atlantic to Spain, financing wars, trade, and imperial expansion while contributing to the growth of international commerce between Europe, Africa, Asia, and the Americas.

Spain established a colonial system intended to secure both economic and political control over its expanding territories. Colonial administrators governed large regions under the authority of the Spanish crown, while settlers established towns, farms, missions, military outposts, and trading centers throughout the Americas.

Religion became deeply connected to Spanish colonization. Catholic missionaries traveled alongside explorers and soldiers, seeking to convert indigenous populations to Christianity. Missions, churches, and religious settlements spread across Spanish-controlled territories, particularly in Florida, the American Southwest, Mexico, and California.

Spanish settlements gradually expanded into portions of what would later become the United States. In 1565, Spain established St. Augustine in present-day Florida, the oldest continuously inhabited European-established city in the continental United States. Spanish influence also spread across the Southwest through exploration, military expeditions, ranching, and mission systems extending into present-day New Mexico, Texas, Arizona, and California.

Relations between Spanish colonists and indigenous populations varied widely across regions. Some indigenous groups formed alliances or trade relationships with Spanish authorities, while others resisted colonization through warfare and rebellion. Forced labor systems such as the encomienda subjected many native populations to harsh exploitation, disease, displacement, and violence under Spanish rule.

The rapid spread of European diseases continued to devastate indigenous societies throughout the Americas. In many regions, population collapse weakened existing political systems and disrupted agricultural production, trade, and social stability long before large-scale European settlement fully expanded inland.

By the end of the sixteenth century, Spain controlled an enormous overseas empire stretching across much of the Western Hemisphere. Yet Spain's dominance also attracted growing competition from rival European powers including France, England, and the Netherlands, each seeking wealth, territory, and influence in North America.

The struggle between these competing empires would shape the future of the continent for centuries and eventually influence the development of the colonies that became the United States.