In the first half of the nineteenth century Americans spread westward across the continent. Living by trapping beaver and trading furs, mountain men explored the mountains, valleys, and trails of the West. In Oregon, missionaries were followed by thousands of pioneers searching for rich farmland, a new life, and adventure. The first large-scale wagon train left Independence, Missouri, for Oregon in 1843. As more settlers moved into the Oregon Territory the United States and Britain clashed over the northern border with Canada. In 1846, the two countries compromised by setting the boundary at 49°N.
In Texas land was offered to people who were willing to bring their families to settle there. By 1830 Americans in Texas far outnumbered Mexicans. The Mexican government became alarmed and began limiting U.S. immigration to and trade with Texas, leading some American settlers to call for independence. At the Battle of the Alamo, a small Texas force held off several thousand Mexican troops for 12 days. Although eventually defeated and killed, their courage inspired others in the fight for freedom. At the Battle of San Jacinto, the Texans surprised the Mexican army and won their independence. In 1845, Texas became part of the United States.
The United States and Mexico did not agree on the southern border of Texas. In addition, the United States wanted to buy New Mexico and California. Many Americans, including President James K. Polk, believed in Manifest Destiny—the United States' right to the land all the way to the Pacific. In 1846, the conflict with Mexico became a war. By winning the war, the United States gained California and the rest of the Southwest.
In 1848 the discovery of gold brought thousands to California, hoping to find
quick riches. Those who arrived in 1849 were called "forty-niners."
By 1850 California was ready to apply for statehood. In the Utah Territory a
religious group settled near the Great Salt Lake. Led by Joseph Smith and later
by Brigham Young, Mormons made the journey west to escape religious persecution.