Since mountains are inhospitable to every phase of the historical movement, they long remain regions of retardation.  Hence to their bordering plains they sustain the relation of young undeveloped lands, so that life in their piedmont belts tends to show for a long time all the characteristics of a new colonial frontier.  The rim of the Southern Appalachians abundantly illustrates this principle even to-day.  During the westward expansion of the American people from 1830 to 1850, the eastern rim of the Rocky Mountains was dotted with trading posts like that of the Missouri Fur Company at the forks of the Missouri River, Forts Laramie and Platte on the North Fork of the Platte, Vrain’s Fort and Fort Lancaster on the South Fork, Bent’s Fort at the mountain exit of the Arkansas River, and Barclay’s in the high Mora Valley of the upper Canadian.  These posts gathered in the rich pelts which formed the one product of this highland area susceptible of bearing the cost of transportation to the far away Missouri River.  Though they developed into way-stations on the overland trails, when the movement of population to California and Oregon in the forties and fifties made the Rocky Mountains a typical highland transit region, yet they long remained frontier posts.[1201] Later the abundant water supply of this piedmont district, as compared with the arid plains below, and the mineral wealth of the mountains concentrated here an agricultural and industrial population.

In Sze Chuan province of western China, the piedmont of a vast highland hinterland shows a similar development.  Here the towns of Matang, Sungpan, Kuan Hsien, and even the capital Chengtu, situated in the high Min Valley at the foot of the mountains walling them in on the west, are emporiums for trade with the Tibetans, who bring hither furs, hides and wool from their plateau pastures, and musk from the musk deer on the Koko Nor plains.[1202] Just to the north, Sian (Singan), capital of the highland province of Shensi, concentrates the fur trade of a large mountain wilderness to the west.  Several blocks on the main street form a great fur market for the sale of mink and other skins used to line the official robes of mandarins.[1203]

[Sidenote:  Mountain carriers.]

Like seas, deserts, and other geographical transit regions, mountains too under primitive conditions develop their professional carriers.  These collect in the piedmont, where highway and mule train cease, and where the steep track admits only human beasts of burden, trained by their environment to be climbers and packers.  These mountain carriers are found on the Pacific face of the coast ranges of North and South America from the peninsula of Alaska to the Straits of Magellan.  They are able to pack from 100 to 160 pounds up a steep grade.  The Chilkoot Indians, men, women and children, did invaluable service on the White Horse and Chilkoot passes during the early days of the Klondike rush.  They had devised