Another of the great movements of the time, which gave a marked impetus to Missouri River navigation, was the War with Mexico. This great event--great not so much in its battles as in its far-reaching results--had been gathering force for years. The influx of American settlers into the province of Texas caused the Mexican Government to adopt repressive measures toward them. This led to successful revolution on the part of Texas, and her independence was finally won by force of arms in 1836. For the next ten years Texas was practically an independent republic seeking annexation to the United States. The question of annexation was the determining issue in the national election of 1844, and the pro-annexationists prevailed. Texas was annexed in the spring of 1845, and in the following December was admitted as a State, against the protest of the Mexican Government. The administration ordered American troops to occupy certain disputed territory claimed by both Mexico and Texas. Collision with the Mexican troops followed: blood was shed, and the United States declared war.
Among the minor operations of the war from a military point of view, but of transcendent importance in their results, were the conquests of New Mexico and California under Harney, Doniphan, and Fremont. All the country so won became a part of the United States. It lay in the pathway of emigration to the West, and must sooner or later have given rise to grave complications. The inevitable issue was precipitated sooner than was expected, but the result must ultimately have been the same. The importance of this acquisition in the history of the nation cannot be overestimated.
The invasion of New Mexico naturally followed the line of the Santa Fe trail. The expeditions were organized on the frontier, mostly at Fort Leavenworth, but also at other points, such as Fort Kearney and St. Joseph. The transportation of troops and supplies to Westport, Leavenworth, and Kearney gave a great deal of work to the Missouri River boats, which thus became an important factor in one of our national wars.
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.