This chapter examines the ways in which the United States expanded its boundaries during the 1840s.
Section 1 discusses how the 1840s saw thousands of Americans migrating westward. These settlers, called overlanders, followed trails to the frontier states of the Midwest, California, and Oregon, seeking a better life and the opportunities for land ownership. Mormons sought religious freedom in Utah, while American missionaries aimed to convert Native Americans in Oregon. A treaty attempted to settle rising conflicts between Native Americans and western settlers. Native Americans agreed to honor specific geographic boundaries, and the United States promised that these territories would belong to the Native Americans forever. This would change, however, as Americans came to believe in Manifest Destinythe idea that Americans were destined to spread across the continent.
Section 2 describes how Americans emigrated to Texas and then fought Mexico to gain independence. In the early 1800s, Mexicoís offers of cheap land lured many American emigrants to Texas. The Mexican government required that Americans live as Mexican citizens, but few settlers adopted Mexican ways. When Mexico enforced its authority on the colony, outraged Texans prepared for war. Texan forces enjoyed some early victories, but Mexican General Santa Annaís superior army soundly defeated the Texans at the Alamo and Goliad. A surprise attack in the Battle of San Jacinto led to the capture of Santa Anna and the end of the war. The newly established Republic of Texas voted in favor of becoming part of the United States. President Jackson, however, was unwilling to upset Northern leaders, who opposed admitting Texas as a slave state.
Section 3 describes how the United States gained new territory after its war with Mexico. Northern leaders, who opposed President John Tylerís push to admit Texas into the Union, warmed to annexation when President James K. Polk introduced an ambitious program that would stretch the nationís borders. When Texas became the twenty-eighth state, old territorial tensions between Mexico and the United States intensified. With war on the horizon, Polk moved to realize his dream of Manifest Destiny. A treaty split the Oregon territory with Great Britain, but Mexico rebuffed Polkís attempts to purchase California. Resigned that no diplomatic solution would end territorial tensions, Polk lured Mexico into war. His successful three-part military strategy gained control of California and secured the capture of Mexicoís capital city. In signing the Treaty of Guadalupe Hidalgo, Mexico gave up much of what became the American Southwest.