In the early to mid-19th century a prevailing movement within the United States was that of Manifest Destiny. This movement would ultimately directly lead to war with Mexico in 1846. The resulting 1848 Treaty of Guadalupe Hidalgo was an important milestone in achieving this “destiny” of sorts for the United States.
The United States had long been interested in extending its borders to the Pacific Ocean. The travels of Lewis and Clark through the newly-purchased Louisiana Territory captivated the minds of Americans, who began dreaming of the vast lands to the west of them.
After Mexico won independence from Spain in 1821, the manifest destiny concept meant the United States and Mexico were on a collision course. At the time, Mexico’s borders extended much further north than they currently do. Several current US states in the American southwest were actually once possessions of Mexico.
President James K. Polk, in office from 1845-1849, was an ardent expansionist. In fact, Polk centered his presidential campaign around territorial expansion and this was a primary reason for his nomination by the Democratic Party.
Early on in his tenure Polk was able to resolve a longstanding dispute with Great Britain over the Oregon Territory. With the northern US boundaries now settled, the US turned its attention to establishing its territorial boundaries to the southwest.
The question over what to do with Texas and the Mexican territories further to the west were next to be addressed.
After years of failed negotiations, war with Mexico was inevitable. The conflict was eventually brought to an end by the Treaty of Guadalupe Hidalgo whose terms provided important context for the events of the following decades within the United States.
Background to the Mexican American War
Central to the Mexican-American War was the issue of what to do with Texas. In 1836 Mexico’s northeastern most territory declared its independence and formed its own state called the Republic of Texas.
Mexico never recognized Texas as an independent state, merely viewing it as a province in rebellion. Further compounding the issue was that Texas deemed its southern border to be at the Rio Grande, while Mexico declared the more northern Nueces river to be the territory’s southern border.
This led to a tricky diplomatic situation for Mexico’s neighbors and other countries. Despite the situation, the United States, France, United Kingdom, and several other nations officially recognized Texas as an independent republic.
The majority of Texas’ population was comprised of American settlers who ultimately wished to be annexed into the United States.
The political situation at the time was untenable as slavery was an extremely divisive issue. Texas was a slave state and generally speaking if a slave state was to be added to the Union, a corresponding free state would also need to be added.
Under President James K. Polk, the United States officially agreed to annex the Republic of Texas in 1845. Texas was admitted into the Union in December 1845, with the free state of Wisconsin added just over two years later.
News of the Texas annexation left Mexico furious. In addition, the southern border dispute had been left unresolved with Mexico still believing the border to be at the Nueces river, while the United States believed the border to be at the Rio Grande.
In a last ditch effort to acquire territory peacefully, Polk sent special envoy John Slidell (known for his later role in the 1861 Trent Affair) to Mexico in November 1845 to attempt to purchase the territories of New Mexico and Alta California.
When Mexico refused the offer, Polk sent troops to the disputed territory near the Rio Grande hoping the presence of those troops would provoke Mexico to attack.
Polk received his wish in April 1846, when Mexican troops attacked US troops near the Rio Grande in the Thornton Affair. Congress would declare war on Mexico in May 1846.
What Was the 1848 Treaty of Guadalupe Hidalgo
Polk initially believed the war would take no more than a few months to conclude. The Americans scored early victories on the battlefield and successfully occupied a majority of the northernmost Mexican territories.
However, Mexico proved resilient and unwilling to capitulate or give in to the American peace terms. Polk thus hoped to “conquer a peace,” or use the superior US military advantage to strong-arm Mexico into giving in to US demands.
By September 1847 the United States occupied Mexico’s capital city. In order to expel the invaders, Mexico would need to agree to a peace treaty. Peace terms would not be straightforward, given Mexico’s weak centralized government and multiple competing factions, each with their own priorities.
Chief Clerk of the State Department Nicholas Trist was sent to negotiate terms for the United States. Ultimately, the United States aimed to secure the exact same territories of New Mexico and Alta California that Slidell had attempted to purchase just two years earlier. This time it came with the cost of thousands of American lives.
After months of discussions Trist proved to be an unskilled negotiator and was recalled by President Polk in November 1847. Trist received the recall and prepared to depart.
As he was about to leave the country, the Mexican government finally committed three commissioners to seriously negotiate peace terms. Sensing an opportunity he could not pass up, Trist immediately resumed negotiations, despite his lack of authority to do so.
On February 2, 1848 Trist signed the Treaty of Guadalupe Hidalgo on behalf of the United States, officially bringing an end to the Mexican-American War.
Trist forwarded on the treaty to Polk by the fastest means available. While Polk was outraged that Trist would negotiate and sign the important treaty on behalf of the US without authorization to do so, the Treaty of Guadalupe Hidalgo contained everything he wanted.
The Senate ratified the Treaty of Guadalupe Hidalgo on March 10, 1848 after modifying one article (Article IX) and eliminating another (Article X).
What did the Treaty of Guadalupe Hidalgo Promise?
The Treaty of Guadalupe Hidalgo stated that Mexico would cede its northernmost territories, which combined to account for about 55% of its prewar territory.
These territories included New Mexico, Alta California (which includes modern-day California, Arizona, Nevada, Utah, and parts of Colorado, Wyoming, and Kansas) as well as extending Texas’ southern boundary to the Rio Grande.
This vast amount of territory is also known as the “Mexican Cession.” In return for all the territory, the US granted Mexico the sum of $15 million, to be paid in annual installments of $3 million upon ratification of the treaty.
The Treaty of Guadalupe Hidalgo also promised and guaranteed certain citizenship and property rights to Mexican citizens living in the newly-acquired US territories.
All Mexican citizens living in the new US territories were given the option to become US citizens, or to remain Mexican citizens and return to Mexico. The Mexicans were given one year to decide and inform the US government, otherwise by default they would become US citizens.
Nearly 90% of the Mexican population in the new US territories would choose to remain and become US citizens. This guarantee of citizenship also came with a promise that the Mexicans would retain their lands and property ownership.
While the original treaty included a provision to honor Mexican land grants (Article X), this article was removed from the ratified version by the Senate. This would pave the way for the US to issue its own land grants to the lands not already occupied or in use.
While Mexicans were granted full citizenship in the territories, westward expansion would soon mean they were outnumbered by white settlers. These original inhabitants oftentimes would face racial discrimination and illegal siezure of property.
Despite the clear terms of the Treaty of Guadalupe Hidalgo, many Mexican-American citizens’ property rights were not honored. To this day there are efforts to address this injustice via Congressional legislation.
Why Was the 1848 Treaty of Guadalupe Hidalgo Important?
The 1848 Treaty of Guadalupe Hidalgo was important for several reasons. First, with the lands acquired as part of the treaty or “Mexican Cession,” the US gained a massive amount of territory.
These territories from Texas to California would help the United States realize its Manifest Destiny ambitions and stretch unimpeded from the Atlantic to the Pacific oceans.
The United States would not stop there with its expansionist tendencies. The years following would see further expansion with the Gadsden Purchase, purchase of Alaska, and annexation of Hawaii, among other future territorial acquisitions.
These acquired territories would soon provide enormous strategic, economic, and commercial benefits to the United States. In fact, just a week before the Treaty of Guadalupe Hidalgo was signed, gold was found in California that would spark a massive population boom and send scores of settlers west along the Oregon Trail.
The additional Pacific coast ports would also help the US to establish additional trade routes with East Asian markets such as China and eventually Japan.
The Treaty of Guadalupe Hidalgo was also important in that it reignited the political arena on the issue of slavery. In the prior decades politicians from both parties tried to avoid the topic of slavery and focus on other issues.
The new territories brought fierce debate regarding the institution of slavery in the territories and whether the Missouri Compromise would continue to apply. The Wilmot Proviso sought to ban slaves in the acquired territories completely.
Though the Proviso was soundly defeated, the ongoing debate would eventually lead to the Compromise of 1850. The further divide among the states would eventually lead to the American Civil War.
As for Mexico, the Mexican-American War and Treaty of Guadalupe Hidalgo was a national embarrassment. The loss of over 55% of its territory and the decisive military defeat and occupation left deep scars in its collective psyche.
Mexico would soon descend into a period of violence and turmoil and experience foreign intervention. Eventually the country would emerge from this turbulence and establish a modern democracy.