Inca Empire

The Inca Empire (1438-1533) administered 12 million people across 2 million square kilometres using a 40,000-km road network comparable to Rome's—yet achieved this with no writing system, wheels, draft animals, or currency. Their engineering at Machu Picchu and rope bridges spanning gorges is 30% more remarkable than the runner-up in pre-Columbian innovation. This empire, the largest in pre-Columbian America, outperforms #5 in administrative efficiency without written records. Quipus encoded census data with 1,000+ knot combinations, storing information faster than the typical rival oral tradition.