Bartering was the earliest form of exchange, followed by the use of livestock, shells, and beads as a medium of exchange. The first coins were created in Lydia in 561 BC, and paper currency was first issued in China in 806 AD. Throughout history, various commodities served as money including wampum, gold, and "Continentals" issued during the Revolutionary War. The US established the dollar and a national bank system in the late 18th century.