MDP - Mexican War (Lesson)

The Mexican War

The Treaty of Guadalupe-Hidalgo ended the Mexican War and increased the territory of the United States. Later in 1853 the Gadsden Purchase established the southern border of the United States with Mexico. Combined with the negotiated division of the Oregon Territory, these acquisitions marked the completion of the United States’ “Lower 48.”

Map of the Mexican Cession territory

Mexican War

The United States annexed Texas after James Polk became president. This takeover resulted in the war between the United States and Mexico. The United States had avoided war with Great Britain over disputes over the Oregon Territory but now faced war with a newly independent Mexico.

The United States asserted that the new border with Mexico following the annexation of Texas should be the Rio Grande River. The Mexican government insisted the new border between an annexed Texas and Mexico was the Nueces River about 150 miles north of the Rio Grande River. President Polk sent troops under the leadership of General Zachary Taylor to the Rio Grande River. Taylor’s troops were attacked in a disputed incident where both sides believed the other had invaded their held lands. This incident sparked the Mexican War. The United States forces under General Taylor’s leadership attacked from the north while General Winfield Scott’s forces landed to the south at Vera Cruz and worked their way north to take Mexico City. The United States swiftly occupied the Mexican territory of California and took Mexico City. As a result, the war quickly came to an end.

Treaty of Guadalupe-Hildago

When the Mexican War began, the Mexican government had only recently established its independence from Spain. During the war Mexico’s government was in disarray. Based on the early victories against Mexico, President Polk sent diplomats to negotiate an end to the Mexican War. Amidst the confusion of the war and turmoil within the Mexican government, U.S. diplomats were able to negotiate a treaty without the consultation of Mexican president Antonio Lopez de Santa Anna. The Treaty of Guadalupe-Hidalgo included the following provisions:

  1. The border between the United States and Mexico was established at the Rio Grande River.
  2. Mexico ceded California and New Mexico to the United States. (These lands represent present-day Arizona, California, and parts of Colorado, Nevada, New Mexico, Utah, and Wyoming).
  3. The United States paid the Mexican government $15 million and settled any claims of American citizens against the Mexican government.

Wilmot Proviso

With the acquisition of the Mexican territories of California and New Mexico the issue of the expansion of slavery into new territories was once again at the forefront of American consciousness. Pennsylvania representative David Wilmot introduced a bill that forbade slavery in any territory acquired from Mexico. The bill was passed in the House of Representatives but failed in the Senate. Despite the failure of the Wilmot Proviso (“proviso” means condition,) sectionalism was evident. Both sides argued their positions. The previous understanding of the Missouri Compromise was challenged. Ultimately while the Wilmot Proviso did not become law, it further revealed the divisive nature of the issue of slavery.

Important People During the Mexican War

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