Spanish expeditions began traveling to areas of North America in the 1500s. Spain already had a growing number of colonies in Mexico and the Caribbean, and there were a series of efforts to secure new territory in areas that would eventually be part of the United States. Spanish explorers traveled northward in an effort to find riches comparable to those of the Aztec, Mayan, and Incan Empires. Missionaries also played a major role in establishing new settlements in northern Mexico, the future U.S. Southwest, and the Pacific region. However, most of the colonial initiatives were initially unsuccessful, as the Spanish failed to find significant sources of gold or silver and were met by intense resistance by indigenous peoples.