On March 10, 1848, the Senate approved a treaty that led to California and much of the Southwest joining the United States. But the man who negotiated the Treaty of Guadalupe Hidalgo was promptly fired on his return to Washington.
Trist was a curious choice to play such a critical role. He was a Virginia aristocrat who lived in Louisiana, and then returned to Virginia to marry Thomas Jefferson’s granddaughter. Trist was the private secretary to Jefferson, and then to President Andrew Jackson.
But Trist was caught up in controversy when he served as the U.S. counsel in Cuba, where he faced British allegations of favoring the slave trade that still existed there. Trist lost his diplomatic position when the Whigs won the election in 1840, but he stayed with his family in Cuba until President James Polk named him as clerk to Secretary of State Buchanan in 1845.
On May 13, 1846, the United States Congress declared war on Mexico after a request from President Polk.
The conflict centered on the Republic of Texas, which opted to join the United States in late 1845 after establishing its independence from Mexico a decade earlier. The U.S. also tried to buy Texas and what was called “Mexican California” from Mexico, which was seen as an insult in Mexico, before war broke out.
Mexico considered the annexation of Texas as an act of war, and after border skirmishes, President Polk asked for a war declaration. In the fighting that followed, the mostly volunteer United States military secured control of Mexico after a series of battles that lasted for about one year and a half.
In April 1847, Buchanan ordered Trist to go to Mexico when the American victory became apparent. When Mexico City fell to United States troops in September 1847, Trist began peace talks with three Mexican negotiators from that nation’s troubled government.
However, Polk wanted the talks to take place in Washington, and he sent orders to Mexico that Trist was recalled as the treaty negotiator. During the six weeks it took for Polk’s orders to make their way to Trist, the diplomat realized he had a brief period to negotiate a treaty with the unstable government in Mexico.
So Trist ignored the recall order and negotiated terms that allowed the United States to buy California (north of the Baja Peninsula), as well as what amounted to half of Mexico’s territory for $15 million.
On February 2, 1848 the Treaty of Guadalupe Hidalgo was signed in Mexico without President Polk’s knowledge. Trist sent a copy of the treaty by the fastest means possible to Polk.
The President was outraged not only at Trist’s insubordination, but that the treaty didn’t even cede more of Mexico’s property to the United States. (Polk wanted Baja California and property to the Baja’s east as part of the deal and had communicated that desire to Trist before negotiations began.)
Polk made the decision to accept the Treaty as written and sent it to the Senate for confirmation, where it was approved by a 34-14 vote and over the objections of abolitionists who feared that slavery would expand into the former Mexico territories.
On Trist’s return to Washington, he was promptly fired by Polk and denied any salary payments earned during treaty negotiations.
Trist’s political career was over at that point, and he took a series of office jobs for the next 22 years. In 1871, Trist received his back pay when he was appointed postmaster of Alexandria, Virginia, during the Grant administration.
He died on February 11, 1874 as a forgotten figure in one of the most significant moments in American history.