What was the Silk Road?

The Silk Road was never a single road. It was a web of caravan routes, mountain passes, oasis towns, and sea lanes connecting East Asia to Central Asia, Persia, India, the Middle East, and Europe, operating in various forms from roughly the second century BCE through the 15th century. Few merchants traveled its full length; goods changed hands repeatedly through intermediaries, with each transfer adding cost, which is precisely why silk was fabulously expensive in Rome. The name itself is a 19th-century coinage by German geographer Ferdinand von Richthofen rather than anything the people using it called it.

What moved along it mattered more than the merchandise. Buddhism traveled from India into China and onward to Korea and Japan; Islam, Nestorian Christianity, and Manichaeism all spread along the same corridors. Papermaking moved west from China, as did gunpowder and the compass, while glassmaking, horses, and new crops moved east. Mathematical and astronomical knowledge circulated in both directions. The routes also carried disease: the Black Death that killed a large fraction of Europe in the 14th century is generally understood to have traveled these networks. The system declined as maritime routes became cheaper and safer and as the Mongol Empire that had secured overland passage fragmented, which is part of what motivated European voyages seeking sea routes to Asia.