Unit 5.3 - Manifest Destiny & the Mexican-American War

Border Dispute with Mexico & Immediate Causes of the War (WOR)

• The US annexation of Texas + Polk’s election angered Mexicans / Polk sent John Slidell to persuade Mexico to sell California & New Mexico territories + settled the dispute between them → mission failed

• Mexican gov refused to sell California / insisted Texas’s southern border was on Nueces River vs. Rio Grande (US)

• Polk ordered Zachary Taylor to move his army across Rio Grande / April 24, 1846, a Mexican army crossed Rio Grande / captured 1 American army & killed 11 → Polk used the incident as excuse to war / Whigs opposed to it but vain / large majority in both houses approved the war

Zachary Taylor & John C. Fremont (WOR)

• A General sent by Polk to lead his army towards the Rio Grande / later on drove Mexican army from Texas & won a major victory at Buena Vista (Feb 1847)

• Backed by only a few dozen of soldiers, few navy officers, & American settlers → overthrew Mexican rule in the region (June 1846) / proclaimed California to be an independent republic

Treaty of Guadalupe Hidalgo (1848) (WOR)

• Nicholas Trist negotiated with Mexico → Rio Grande is the southern border of Texas + California & New Mexico belongs to the US

• Some Whigs opposed it → immoral effort to expand slavery

• Senate finally ratified it

Wilmot Proviso (WOR)

• David Wilmot proposed an appropriations bill be amended to forbid slavery in any territory acquired from Mexico → appealed to many voters & lawmakers / preserve lands for Whites settlers & protect them from competition with enslaved labor

• Passed the House (populous Northern states had greater power) / defeated in the Senate (Southern states had greater influence there)

Explain the reasons & results of the Mexican American War.

The Mexican War was caused over the dispute about territories between the US and Mexico. While the US wants the southern border of Texas to start from Rio Grande, the Mexicans refuted the idea. Using the excuse that Mexico attacked American army, the US raised war against them. As a result, America won and gained Texas, California, and New Mexico.