It is impossible to understand the history of the United States without some knowledge of the exploration which was accomplished during the early part of the nineteenth century. The westward movement of the American people, which followed the Louisiana purchase, was carried out after the explorers had done their work as a necessary preliminary. The annexation of Texas in 1845, of the Oregon region in 1846, and of the Spanish south-west, after the war of 1848, were a natural result of exploration and subsequent settlement. The movement of western settlers followed so closely on the heels of the trappers and explorers, that the importance of exploration has not always been realised.
This book has attempted to relate the exploration of these years to Geography. The historical order of the discoveries was, in a sense, determined by geographical factors. The exploration of the region was partly accomplished by the trading pioneers of the fur trade. It can be said that exploration and trade resulted in the settlement of the region, particularly in Oregon, California, and the Salt Lake district. The history of the settlement of the region has not been discussed, although it must be realised that exploration and settlement are two closely related subjects. The two most important discoveries, from the point of view of settlement, were those of the South and the Truckee Passes. Through these passes and along the routes laid down by the explorers and trappers poured a great stream of migration to Oregon and to California. Between the years 1842 and 1846 large numbers of American pioneer settlers reached the Oregon country by way of the Oregon trail, while in later years thousands of emigrants followed the old trails that led them to the gold of California.1 The Oregon trail, the____________________