the head of the Great Kanawha, and that he opened a way from the Potomac to the Ohio. How important these strategic points are now considered is evident from the fact that a railway crosses the mountains at each of them; the New York Central, the Baltimore and Ohio, the Pennsylvania, and the Chesapeake and Ohio cross the first great divide in the eastern portion of our country on routes selected centuries ago by the plunging buffalo. One of the most interesting of specific examples of a railway following an ancient highway of buffalo and Indian is to be found on the Baltimore and Ohio. However, Frank G. Roe disputes this theory – and its wider application – in "The 'Wild Animal Path' Origin of Ancient Roads". Some suggest that the portage routes of North American indigenous peoples followed "the game trails the animals had made around rough water. ... [And] as centuries passed, well-trodden paths were made, winding among the rocks, and, by the easiest of grades, over or around hills". Asia China The Silk Road was a major trade route between China and India, Europe, and Arabia. It derives its name from the lucrative trade in silk carried out along its length, beginning in the Han dynasty (207 BCE–220 CE). The Han dynasty expanded the Central Asian section of the trade routes around 114 BCE through the missions and explorations of the Chinese imperial envoy Zhang Qian. The Chinese took great interest in the safety of their trade products and extended the Great Wall of China to ensure the protection of the trade route. Prior to the Silk Road an ancient overland route existed through the Eurasian Steppe. Silk and horses were traded as key commodities; secondary trade included furs, weapons, musical instruments, precious stones (turquoise, lapis lazuli, agate, nephrite) and jewels. This route extended for approximately . Trans-Eurasian trade through the Steppe Route precedes the conventional date for the origins of the Silk Road by at least two millennia. See also the Northern Silk Road, the Southern Silk Road: Through Khotan, Tea Horse Road. The Shudao (), or the "Road(s) to Shu", is a system of mountain roads linking the Chinese province of Shaanxi with Sichuan (Shu), built and maintained since the 4th century BC. Technical highlights were the gallery roads, consisting of wooden planks erected on wooden or stone beams slotted into holes cut into the