 Their use antedated the move west into the Rockies as colonial Americans sent out the first fur trappers and explorers past the Appalachians who were then followed west by high-risk-taking settlers by the 1750s (such as Daniel Boone) who led an increasing flood of emigrants that began pushing west over into southern New York, and through the gaps of the Allegheny into the Ohio Country (the lands of western Province of Virginia and the Province of Pennsylvania), into Tennessee and Kentucky before and especially after the American Revolution.In the nineteenth century, twenty-mule teams, for instance, were teams of eighteen mules and two horses attached to large wagons that ferried borax out of Death Valley from 1883 to 1889.The wagons were among the largest ever pulled by draft animals, designed to carry 10 short tons (9 metric tons) of borax ore at a time.