• By 1525, had population of more than 6 million people
• Originated in Cuzco Valley, expanded militarily in mid-15th century
• Used traditional Andean social customs and economic practices
• Empire built on mita labor, forced service to ruler
• Prosperity and military strength depended on llamas and alpacas
• As empire expanded, generally left local rulers in place
• On November 16, 1532, first encounter between Inca and Spanish