Scarcely had the treaty of Guadaloupe Hidalgo, which closed the war, been signed, when an event took place in the newly acquired territory which completely revolutionized the situation of things in the West. This was the discovery of gold in California in 1848. Emigration had been moving to the coast, principally into Oregon, for the previous six years. The first large movement took place in 1843. In 1845 and 1846 several parties crossed the Sierras into California, and there was a strong nucleus of American settlers there when the conquest came. The discovery of gold swelled this incipient stream into a mighty river. From every part of the world, by land and by sea, the rush to California began. The overland movement was one of the greatest and most wonderful migrations of a people which history records. It ran in full strength for several years, beginning in 1849, and by 1854 a vast but unknown number had crossed the plains. There were various starting points from the Missouri River in this migration, although the different routes united before Fort Laramie was reached. Westport, Leavenworth, Fort Kearney, and Omaha became initial rendezvous, and a great deal of traffic for the emigrants was done by the river boats from St. Louis to these points. Following the three great movements just described came the period of government exploration of the entire Western country, and the search for practical railroad routes across the mountains. Large exploring parties were sent into the field, and bodies of troops were dispatched to the Pacific Coast and to distant points in the interior. [Sidenote: LARGE RIVER BUSINESS.] The aggregate amount of business brought to the lower Missouri from these various causes was large. Viewed from the standpoint of transportation, the Western country in that day can be likened in shape to a fan. The handle was that portion which extended from St. Louis to the mouth of the Kansas River. Thence the various routes to all parts of the country diverged along the arms of the fan, which were outspread from Santa Fe on the south to Fort Union on the north. Most of the business below the point of divergence was done by steamboat. Vessels in large numbers plied the river over this first four hundred miles, and the amount of freight and passenger traffic carried by them was very great. Boats departed daily from St. Louis, carrying an almost inconceivable variety of articles for use of the emigrants, and nearly as large a variety of emigrants themselves. To one who witnessed this business in the noontide of its activity, it would have seemed scarcely possible that another generation should witness its total extinction. [Sidenote: LA BARGE AND THE MORMONS.]