Persia's Royal Road carried a message 1,500 miles in nine days

Long before the postal service, the Achaemenid Persian Empire ran on a road. The Royal Road, perfected under Darius I around the 5th century BCE, stretched more than 1,500 miles (2,400 km) from Susa in the Persian heartland to Sardis near the Aegean coast.

Its genius was the relay. Couriers handed messages from one fresh horse and rider to the next at stations spaced about a day apart, so a dispatch could cover the whole route in roughly nine days — a trip that took an ordinary traveller about three months on foot.

The system so impressed the Greek historian Herodotus that he wrote there was nothing in the world faster than these Persian couriers, whom “neither snow, nor rain, nor heat, nor gloom of night” could stop. Centuries later, a version of that line was carved over a New York post office.