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Eric Gay, AP
International Bridge I, foreground, and International Bridge 2 cross the Rio Grande at Laredo, Texas. A treaty between Mexico and the United States, signed Feb. 2, 1848, established the border as the Rio Grande.

On Feb. 2, 1848, the United States and Mexico signed the "Treaty of Peace, Friendship, Limits and Settlement between the United States of America and the Mexican Republic," known commonly as the Treaty of Guadalupe Hidalgo. The treaty ended the Mexican-American War and established the current border between the two nations.

The Mexican-American War began in 1846 after a border dispute between Texas and Mexico. Many prominent Americans opposed the war, such as Whig congressman Abraham Lincoln and former president John Quincy Adams. The Mexican-American War played into the increasing North/South divide that would eventually tear the nation apart during the Civil War. Many Northerners feared that if the United States won the war against Mexico, it would strengthen the Southern slave states.

In its opening stages, General Zachary Taylor led U.S. forces into northern Mexico from Texas and proved victorious in multiple battles. Mexican President and General Antonio Lopez de Santa Anna suffered a crushing defeat from Taylor's forces at the February 1847 Battle of Buena Vista. In March, General Winfield Scott landed at Veracruz, Mexico City's chief port on its eastern shore. After marching up Mexico's national highway toward Mexico City, Scott encountered the entrenched position of Santa Anna and his army at Cerro Gordo.

Rather than fight the Mexicans head on, Scott was able to outflank the Mexican positions by moving his force through what many had considered to be impassable terrain around it. His chief scout who located a trail around the Mexican army was a young captain of engineers, Robert E. Lee. Outflanked, the Mexicans retreated toward Mexico City, where a series of battles ultimately ended in the U.S. victory.

Confident of victory from the beginning, President James K. Polk dispatched diplomat Nicholas Trist to negotiate an end to the war on favorable terms for the United States. A staunch Democrat, Polk selected Trist not only for his ability in the realm of diplomacy, but also for his Democratic credentials. A Virginian, Trist had married a granddaughter of Thomas Jefferson and had served for a brief period as a secretary to President Andrew Jackson. Surely Trist was man who knew how to toe the party line.

Trist arrived in American-occupied Veracruz in May 1847 and forwarded a letter to Scott, whose army was dealing with events at Cerro Gordo. Uninformed of Trist's mission beforehand, the ever-suspicious Scott believed that the diplomat had arrived to usurp the direction of the war. This reflected the fact that Scott, a Whig, had political ambitions and feared that President Polk was trying to eclipse the general's battlefield success by diplomatic maneuver. In any event, both Scott and Trist suffered from no shortage of ego, and their relationship remained rocky for several months.

By summer, Trist had taken ill and a surprisingly compassionate Scott sent the diplomat jars of guava marmalade, which happened to be Trist's favorite. The two began to work together and by August 20, with the gates of Mexico City before him, Scott sent a demand to Santa Anna to send peace commissioners to negotiate with Trist. Though the Mexicans broke off the initial round of talks, American military power and their own declining position ensured that they were soon resumed.

About the time Trist began to negotiate in earnest with the Mexican commissioners, Polk began to believe that the diplomat had strayed too far from his instructions. Additionally, the newly formed cordiality between Scott and Trist perhaps further soured the president on his chief negotiator. Polk instructed Secretary of State James Buchanan to send a letter recalling Trist from Mexico and publicly stated that he had recalled Trist before an address to Congress in December.

Meanwhile, the ever-unstable Mexican government saw a couple of regime changes, and new commissioners negotiated with Trist. With the Mexicans not yet aware of his recall and wanting to wrap up a treaty before he was forced out of his position, Trist stated that a treaty must be signed by the first of February 1848.

In his book, “Polk: The Man Who Transformed the Presidency and America,” historian Walter R. Borneman wrote: “As it was, it took until February 2 for all details to be agreed upon and copies completed in both English and Spanish. While the negotiations had been held in the capital, the Mexican commissioners requested that the official signing take place at the nearby town of Guadalupe Hidalgo, and by that name the treaty came to be called.”

Ultimately, Polk did not get everything he wanted out of the treaty, such as Mexico's Baja Peninsula, yet the United States did gain quite a bit of territory at Mexico's expense. In his book “To the Halls of the Montezumas,” historian Robert W. Johannsen described the provisions:

“The Rio Grande (River) was recognized as the boundary of Texas, a New Mexico and California — over half a million square miles of territory — were ceded to the United States. On its part, the United States assumed the unpaid claims of American citizens against the Mexican government and agreed to pay Mexico the sum of $15,000,000.”

The treaty firmly established America's southern and Mexico's northern border. It also fulfilled an idea that had existed for decades in the American mind, that of Manifest Destiny — the idea of the United States stretching from the Atlantic to the Pacific oceans, creating an American continent.

When news of the treaty first arrived in Washington a few weeks after the signing, Polk found himself in an awkward situation. He had publicly recalled his chief negotiator, and now wondered if the treaty, which he generally approved of, had been created with the proper legal authority. Polk considered the alternative, a continuation of a war already won, and deemed it politically damaging. He decided to forward Trist's treaty to the Senate for debate and ratification.

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In his book, “The Rise of American Democracy: Jefferson to Lincoln,” historian Sean Wilentz wrote: “Senate approval of the treaty was not assured. Several members of the Foreign Relations Committee, of both parties, objected that Trist had had no powers to negotiate on behalf of the government once he had been recalled. Some Democrats thought the agreement gave the Untied States far too little territory; some Whigs … thought it gave the United States far too much. But as secret deliberations continued, the prospect of finally ending the war overcame all other considerations.”

Following two weeks of debate, the Senate voted 38 to 14 to ratify the treaty. The treaty had supporters and detractors from both North and South, both Whigs and Democrats. President Polk officially declared that the treaty would go into effect on July 4, 1848, an Independence Day that was celebrated with unusual felicity that year.

For a wonderful, fictionalized account of the Mexican-American War and Trist's mission, read Jeff Shaara's superb “Gone For Soldiers.”

Cody K. Carlson holds a master's degree in history from the University of Utah and currently teaches at SLCC. He has also appeared on many local stages, including Hale Centre Theatre and Off Broadway Theatre. Email: ckcarlson76@gmail.com