The Treaty of Guadalupe Hidalgo — also known as the “Mexican Cession” — ceded 55% of Mexico’s territory to the United States, including Nevada, Utah, and portions of California, Arizona, and New Mexico. Mexico also dropped all claims to Texas. The acquisition of the new territory allowed the United States to move toward fulfilling Manifest Destiny, which was finalized with the Gadsden Purchase in 1853.
President Polk, Manifest Destiny, and the Treaty of Guadalupe Hidalgo
James K. Polk was the 11th President of the United States. Polk is famous for promising to serve one term in office and dedicate his time to the fulfillment of America’s Manifest Destiny.
During the 1844 election, Polk, the Democratic Party candidate, declared that Texas should be “re-annexed” and all of Oregon “re-occupied.” Polk also intended to acquire California and was willing to go to war with Mexico to make it happen.
By the time Polk took office in 1845, Congress had authorized the Annexation of Texas. Mexico was outraged over the move and threatened war, because of an ongoing border dispute between Texas and Mexico.
Polk sent an envoy, Congressman John Slidell to Mexico, to negotiate the purchase of California and New Mexico — which accounted for more than half of Mexico’s territory. The offer was rejected.
Polk responded with two expeditions.
The first was a scientific expedition led by John C. Frémont who went to California. Although the official purpose of Frémont’s expedition was to explore and map the region, there is speculation he was there to incite rebellion against the Mexican government. Frémont became involved in the Bear Flag Revolt, which led to the establishment of an independent government in California.
The second was a military expedition led by General Zachary Taylor who organized an “Army of Observation” to keep watch over the area near the Rio Grande River that was claimed by both Mexico and Texas. After American troops were attacked in the Thornton Affair, Polk and Congress declared war on Mexico.
American forces, led by Taylor, Winfield Scott, and Stephen Watts Kearny, won repeated victories and occupied Mexico City. Finally, in 1848, Mexico ceded New Mexico, California, and more to the United States in the Treaty of Guadalupe Hidalgo.
1. The Treaty of Guadalupe Hidalgo Helped Expand the United States
President James K. Polk oversaw the United States’ significant territorial expansion. He achieved this by annexing Texas in 1845, negotiating the Oregon Treaty with Great Britain in 1846, and concluding the Mexican-American War in 1848. The war ended with the signing and ratification of the Treaty of Guadalupe Hidalgo in 1848.
These actions brought under U.S. control future states like Texas, California, Nevada, New Mexico, Arizona, Utah, Washington, and Oregon. Additionally, parts of what would later become Oklahoma, Colorado, Kansas, Wyoming, and Montana became part of the United States.
It was the largest territorial expansion of the United States since the 1803 Louisiana Purchase.
2. Treaty of Guadalupe Hidalgo Dates
- Signed — The Treaty of Guadalupe Hildago was signed on February 2, 1848.
- United States Ratification — The U.S. Senate ratified the Treaty of Guadalupe Hildago on March 10, 1848.
- Mexico Ratification — The Mexican government ratified the Treaty of Guadalupe Hildago on March 19, 1848.
- Effective — The treaty went into effect on May 30, 1848.
3. The Texas Revolution was a Key Event Leading to the Treaty of Guadalupe Hidalgo
Following the Texas Revolution, Texas was an independent republic. However, President Martin Van Buren refrained from annexing Texas due to Mexican threats of war. Diplomatic recognition was granted to Texas, but no further action was taken until 1844 when President John Tyler resumed negotiations with the Republic of Texas.
These negotiations led to the Treaty of Annexation on April 12, which prompted Mexico to sever diplomatic ties with the United States. However, Tyler failed to secure Senate ratification for the treaty in June.
Just before leaving office, Tyler attempted again, this time using a joint resolution of Congress. With President-elect Polk’s support, the resolution passed on March 1, 1845, and Texas officially became a part of the United States on December 29.
4. A Border Dispute Was a Cause of the Mexican-American War
Despite Mexico not acting on its threat of war over Texas annexation, relations remained strained due to disputes over the Texas-Mexico border. Texans asserted that their state encompassed large parts of modern-day New Mexico and Colorado, as well as the western and southern regions of present-day Texas, including the Rio Grande River. In contrast, Mexico contended that the border was limited to the Nueces River, located north of the Rio Grande (see Mexican-American War Causes).
5. Mexico Refused to Negotiate with the United States
In July 1845, President Polk instructed General Zachary Taylor, the commander of the U.S. Army in Texas, to move his forces into the disputed lands between the Nueces and Rio Grande rivers.
In November of that year, Polk sent Congressman John Slidell to Mexico, aiming to negotiate the purchase of the disputed border areas and the territories now known as New Mexico and California.
6. The Thornton Affair Triggers the Mexican-American War
When Slidell’s mission failed in May 1846, President Polk seized upon news of skirmishes between Mexican troops and Taylor’s army in the disputed territory to rally Congressional support for a declaration of war against Mexico. As a result, on May 13, 1846, the United States officially declared war on Mexico (see Mexican-American War Timeline).
7. Polk Tried to Stop the Negotiations for the Treaty of Guadalupe Hidalgo
Following the capture of Mexico City in September 1847, Nicholas Trist, who served as the chief clerk of the Department of State and was appointed as Polk’s peace emissary, initiated negotiations for a peace treaty with the Mexican Government, pursuing terms similar to those previously pursued by John Slidell.
However, President Polk began to have concerns about Trist’s approach.
- He worried that Trist might not push for terms that were strong enough from the Mexican perspective.
- Additionally, Polk was troubled by Trist’s close friendship with General Winfield Scott, a prominent Whig figure who was considered a strong contender for the Whig party’s presidential nomination in the upcoming 1848 election.
- Furthermore, some expansionist Democrats were advocating for the complete annexation of Mexico due to the ongoing war.
- As a result of these concerns and circumstances, President Polk decided to recall Nicholas Trist in October.
8. Important Details of the Treaty of Guadalupe Hidalgo
Despite the recall order, Nicholas Trist, believing he was close to an agreement, continued negotiations and presented President Polk with the Treaty of Guadalupe-Hidalgo on February 2, 1848, in Mexico City.
This treaty had significant terms:
- Mexico ceded approximately 525,000 square miles, which accounted for 55% of its prewar territory, to the United States.
- In exchange, the United States agreed to make a lump sum payment of $15 million to Mexico.
- Additionally, the U.S. Government committed to assume up to $3.25 million worth of debts that Mexico owed to U.S. citizens.
These terms marked the conclusion of the Mexican-American War and had a substantial impact on the territorial boundaries of both nations.
9. Polk Accepted the Treaty of Guadalupe Hidalgo and Submitted it to the Senate
President Polk, though inclined towards a more extensive annexation of Mexican territory, recognized that prolonging the war could lead to detrimental political consequences. Therefore, he made the strategic decision to present the treaty to the Senate for ratification. While the Senate saw considerable opposition to the treaty, on March 10, 1848, it passed by a narrow margin, with a vote of 38 in favor to 14 against.
10. The Treaty of Guadalupe Hidalgo Intensified the Debate Over Slavery
The Treaty of Guadalupe Hidalgo had a profound impact on the issue of slavery in the United States.
In August 1846, Congressman David Wilmot introduced a rider to an appropriations bill known as the “Wilmot Proviso.” This proviso stipulated that in any territory acquired by the United States as a result of the war against Mexico, “neither slavery nor involuntary servitude shall ever exist.”
Although Southern senators were successful in blocking the adoption of the Wilmot Proviso, it ignited a significant political controversy. The question of whether slavery could expand into newly acquired territories continued to simmer and fester in the United States until the ultimate defeat of the Confederacy in 1865, during the American Civil War.
Treaty of Guadalupe Hidalgo APUSH Definition
The Treaty of Guadalupe Hidalgo for APUSH is defined as an agreement signed on February 2, 1848, marking the end of the Mexican-American War. Under the treaty, Mexico ceded a vast amount of territory to the United States, including California, New Mexico, Arizona, Texas, and more, in exchange for $15 million in compensation. This treaty not only expanded U.S. territory significantly but also ignited debates over slavery in the newly acquired territories. The Treaty of Guadalupe Hidalgo remains a pivotal document in U.S. history, shaping the nation’s boundaries, demographics, and political landscape in the mid-19th century.
The Treaty of Guadalupe Hidalgo is part of APUSH Unit 5: 1844–1877.