The Mexican-American War - The U.S. Expands

The video introduces Westward Expansion, focusing on the 19th-century acquisition of lands between the Mississippi River and the Pacific Ocean. It highlights the movement of American settlers, including those with enslaved people, into Texas, leading to a Texas Independence Movement. The desire for Texas to join the U.S. as a slave state is discussed, setting the stage for the annexation and further territorial acquisitions.

Andrew Jackson and other politicians foresaw two main problems with annexing Texas: Mexico's potential desire to reclaim the territory and the debate over extending slavery into new western lands. However, the concept of Manifest Destiny, the belief in God's will for American expansion to bring freedom and prosperity, became a strong counter-argument. Other reasons for annexation included the desire for ocean-to-ocean borders, Southern desire to expand slavery, and the spread of Protestant faith. In 1844, James K. Polk won the presidency on a platform of annexing Texas and expanding into New Mexico, California, and Oregon, leading to Texas's annexation in 1845.

Following Texas's annexation, a dispute arose over its southern border, with Mexico claiming the Nueces River and Texas claiming the Rio Grande. President Polk, an expansionist, sought to acquire more territory. He sent General Zachary Taylor with troops to the disputed area and offered to buy the region, along with New Mexico and California, for $30 million. Polk intentionally made an offer he knew Mexico would reject, aiming to portray Mexico as hostile. When the offer was rejected and Ambassador John Slidell was asked to leave, Polk ordered Taylor to cross the Nueces, provoking a Mexican attack on American soldiers. This incident provided Polk with the justification to declare war on Mexico in 1846.

During the war, a small American group in California staged the Bear Flag Revolt, declaring independence. After two years, the better-trained American Army defeated Mexico. While the U.S. could have annexed all of Mexico, concerns over incorporating a large, culturally distinct population led to the Treaty of Guadalupe Hidalgo in 1848. This treaty resulted in the Mexican Cession, where Mexico ceded over half its territory, including modern-day California, Nevada, Utah, and parts of Arizona, New Mexico, Colorado, and Wyoming, for $15 million. Five years later, the Gadsden Purchase in 1853 further expanded U.S. land in Arizona and New Mexico, completing most of the westward expansion map.

The video summarizes that despite early concerns, the spirit of Manifest Destiny and President Polk's influence led to the annexation of Texas in 1845. Polk orchestrated the conflict that led to the Mexican-American War in 1846, resulting in significant territorial gains through the Treaty of Guadalupe Hidalgo and the Gadsden Purchase. These acquisitions largely completed the westward expansion of the United States, with only the Oregon country remaining for future exploration.