Today marks the anniversary of the signing of the Treaty of Guadalupe Hidalgo formally ending the Mexican-American War. As you might have guessed, the treaty was signed in Guadalupe Hidalgo, which is just outside of Mexico City. Under the terms of the treaty the United States received California, New Mexico, Arizona, Utah, and Nevada. In return, Mexico received $15 million and Washington agreed to pick up the tab for $3.25 million in claims that U.S. citizens had against the Mexican government.
I am not flagging the anniversary because it’s how we ended up with Las Vegas, though I suppose that’s a benefit. Rather, the Treaty of Guadalupe Hidalgo is significant because it was negotiated by a U.S. diplomat in direct defiance of the president of the United States. Add in a heavy dose of domestic politics, and you have a diplomatic negotiation for the ages.
First some background. The United States declared war on Mexico on May 13, 1845, shortly after Mexican troops killed eleven Americans north of the Rio Grande. The war’s origins were shrouded in controversy; in many ways it was the nineteenth century version of the Gulf of Tonkin Resolution. President Polk had been spoiling for a fight, and he used the clash, which the Americans in some ways provoked, to go to war. Polk’s allies rushed the declaration of war through Congress, refusing to allow members who wanted more time and information to speak.
Polk expected a quick victory. He didn’t get it. Despite losing several major battles, the Mexican government, led by Antonio López de Santa Anna, who is best remembered by American schoolchildren as the villain at the Battle of the Alamo, refused to negotiate unless U.S. troops left Mexican soil. Polk tried to break the stalemate in the spring of 1847 by sending Nicholas Trist, the State Department’s chief clerk to Mexico. Trist knew some Spanish, having once been posted to Havana. He was also, like Polk, a Democrat, so he was presumed to be loyal to the president. In particular, Polk wanted Trist to keep an eye on Gen. Winfield Scott, who Polk (rightly) suspected of harboring presidential ambitions.
Trist’s efforts didn’t produce much that summer even though by mid-September Scott’s troops had captured Mexico City and forced Santa Anna from power. That mattered less to Polk, though, than what he saw as signs that Trist could not be trusted. Trist had forwarded to Washington rather than rejected out of hand a Mexican proposal to set the border not at the Rio Grande as the Americans had insisted all along but further north at the Nueces River. Perhaps worse, Trist had struck up a close friendship with General Scott. So in early October, Polk ordered Trist to return to Washington.
Trist received his recall in mid-November, and he did what would seem unthinkable: He refused to stop negotiating. He believed that the new Mexican government would agree to the treaty terms that Polk had instructed him to negotiate. He also worried that if he returned home that the next U.S. envoy might ask for even more from Mexico. He believed that tougher terms would be unacceptable to the Mexicans and condemn the United States to a bloody and protracted guerrilla war. As he later explained it:
My object was…to make the treaty as little exacting from Mexico, as was compatible with its being accepted at home.
So Trist wrote Polk a sixty-five page letter explaining why he intended to ignore his recall and finish the job.
Trist’s letter arrived in Washington in mid-January. Polk did not take the news well. He wrote in his diary that the letter
was dated on the 6th of Decr. last, and is the most extraordinary document I have ever heard from a Diplomatic Representative . . . . His despatch is arrogant, impudent, and very insulting to his Government, and even personally offensive to the President. He admits he is acting without authority and in violation of the positive order recalling him. It is manifest to me that he has become the tool of Gen ‘l Scott and his menial instrument, and that the paper was written at Scott’s instance and dictation. I have neer in my life felt so indignant, and the whole Cabinet expressed themselves as I felt….If there was any legal provision for his punishment he ought to be severely handled. He has acted worse than any man in public employ whom I have ever known. His despatch proves that he is destitute of honour or principle, and that he has proved himself to be a very base man.
Polk hated the Treaty of Guadalupe Hidalgo because General Scott’s capture of Mexico City had convinced him he could squeeze more out of the Mexicans. But the treaty’s provisions matched the terms he had initially given Trist. And that meant that Polk had a political problem. Public opposition to the war was growing. In late December 1847, an obscure Illinois congressman named Abraham Lincoln offered the so-called Spot Resolution demanding to know exactly where on U.S. soil the first American blood was shed. Two weeks after that, the House passed a resolution declaring that the war had been “unnecessarily and unconstitutionally begun." Polk summarized his dilemma for his cabinet:
I were now to reject a treaty made upon my own terms, as authorized in April last, with the unanimous approbation of the Cabinet, the probability is that Congress would not grant either men or money to prosecute the war.
That would mean, of course, that the United States would end up with less territory than it gained under the treaty. Polk was unwilling to test his prediction about congressional behavior. On February 22, 1848, he submitted the Treaty of Guadalupe Hidalgo to the Senate for its advice and consent.
Polk may not have gotten his way on the treaty with Mexico, but he exacted his revenge on Trist. He refused to pay Trist’s salary or reimburse his expenses. Trist lost his State Department job, plunging him into poverty. He wouldn’t find redemption until after the Civil War when Congress reimbursed him for his lost salary and unpaid expenses. President Ulysses S. Grant, who fought with great distinction in the Mexican-American and thought it "the most unjust war ever waged by a stronger against a weaker nation”—made him postmaster of Alexandria, Virginia, just across the Potomac from Washington.