The Inca Empire was the largest empire in pre-Columbian America. In the 15th century it incorporated a large portion of western South America, centered on the Andean Mountains. From their mountain capital at Cusco, the Incas ran an efficient government. The Inca Empire was a federal systam consisting of central government with 4 quarters. Each of them had local governor and it was divided again into smaller districts. The Empire was 2,800 miles long. A complex system of roads and suspension bridges was built through out the Empire. The Incas used those roads for trade, communications and troop movements. Roughly 15,000 miles of road linked the Inca Empire together.