Lesson 7: Manifest Destiny in California and the Southwest

Key Idea

Conflict with Mexico grew after the United States annexed Texas in 1845. The two nations disputed the official border, and President James K. Polk sent troops into the contested region. A clash between soldiers there sparked the Mexican-American War in 1846.

The United States achieved a decisive victory. The conflict ended in 1848 with the Treaty of Guadalupe-Hidalgo. In this agreement, Mexico was forced to give up a vast territory known as the Mexican Cession. This land included modern-day California, Nevada, Utah, and Arizona.

Key Idea

The Mormons faced violent religious persecution in the eastern United States. After their leader was killed in 1844, they sought a safe refuge where they could practice their faith without interference.

Led by Brigham Young, thousands of Mormons began a difficult journey west in 1847. They settled in the harsh, dry valley of the Great Salt Lake, which was then part of Mexico. Through teamwork and irrigation, they transformed the desert into a thriving community.

Key Idea

The 1848 discovery of gold in California triggered a massive migration. Thousands of prospectors, known as Forty-niners, rushed to the territory. This sudden population boom created an urgent need for an organized government.

By 1849, Californians wrote a constitution that banned slavery and applied to join the Union as a free state.

Key Idea

The Gold Rush's population explosion quickly led to California's request for statehood. In 1850, California was admitted to the Union as a free state. This decision disrupted the delicate balance of power in Congress between free and slave states.

This rapid growth also had a devastating impact on the Californios, the region's long-time Mexican residents. The Land Law of 1851 forced them to prove ownership of their land in U.S. courts. Many lost their property through costly legal battles, forever changing the social landscape of California.