From 1822, when the first wagons were used in the Santa Fe trade, until 1880, when the completion of major railroad lines made the wagon train all but obsolete, wagon freighting was essential to the trade, settlement, and growth of the American West, from the Missouri Valley to the Great Basin.             Freighters carried goods to and from Santa Fe, bringing in much of the trade goods for the settlements of the Mountain West. Under contract to the government, they supplied the army sent to fight Mexicans and American Indians. Without the wagonmasters, the flow of gold from the mines of Colorado and Montana, which proved essential during the Civil War, would have been delayed at least a decade.             The Wagonmasters is the first comprehensive account of this colorful bygone industry and the men who worked the wagon trains--bullwhackers and mule skinners. A breed apart, they developed their own customs and language, greatly enriching American speech. The business was hard, dirty, and dangerous, but the wagon freighters, like the U.S. mail, almost always came through.