After its conquest of the Aztecs and Incas, Spain neglected its Caribbean holdings. Hispaniola's sugar plantation economy quickly declined. Most Spanish colonists left for the silver-mines of Mexico and Peru, while new immigrants from Spain bypassed the island. Agriculture dwindled, new imports of slaves ceased, and white colonists, free blacks, and slaves alike lived in poverty, weakening the racial hierarchy and aiding ''intermixing'', resulting in a population of predominantly mixed Spaniard, Taíno, and African descent. Except for the city of Santo Domingo, which managed to maintain some legal exports, Dominican ports were forced to rely on contraband trade, which, along with livestock, became one of the main sources of livelihood for the island's inhabitants.