Though frustrated on Cuba, American expansionists had other locales to draw their eyes. The nation just recently took away a third of Mexico, why not take more? In fact, the United States might have done just that. The Polk administration first wanted only California, New Mexico, and resolution of the Texas border dispute in its favor. One might expect that massive expanse of land, as large as all Western Europe, to satisfy the expansionists. If they could make five new slave states from Texan territory, they could certainly make at least five or six more from the Mexican Cession. Polk’s instructions to his negotiator in Mexico City, Nicholas Trist, stated just that aim.
Battlefield success whetted territorial appetites and filled dreams with visions of a still grander acquisition. Mexico proved so weak and the United States so strong, why not take the whole country? A serious movement formed in the Democratic Party for just that even as the Whigs rallied behind No Territory. But the Democracy might concede and suffer the continued existence of a Mexican state at the low price of additional territory south of the Rio Grande. With those Manifest Destiny dreams spurring him on, Polk recalled Trist in October, 1847.
After wrestling with Santa Anna for some time to secure merely half his country for the United States, Trist felt he had just began to make progress and so wrote back a long letter explaining why he chose to remain. Polk’s envoy depart from his instructions in one other way: Polk meant for him to collect Baja California in addition to Upper California. Trist demurred.
When the Treaty of Guadalupe-Hidalgo came into Polk’s hands in February, 1848, he overcame his initial impulse to toss it and submitted it to the Senate with the implicit threat that if the Whigs blocked its ratification, he might go back and get still more land from Mexico on top of making them pay the political cost of opposing expansion.
The expansionists had one last go of it in the Senate. Jefferson Davis, with the support of both Texan senators, Stephen Douglas of Illinois, a few other Northerners and several Southern senators proposed to take all of northeastern Mexico by amendment. The Democracy’s cooler heads, and Calhoun who opposed taking more of Mexico on the grounds that it simply had too many Mexicans for a white man’s Union, prevailed. The amendment’s opposite party twin, a Whig initiative to remove all the Mexican Cession and take only the disputed Texan territory, likewise failed.
But Mexico in the 1850s did not look any stronger than Mexico in the late 1840s when the United States easily dismembered it. Another war, or a handy filibuster on the Texas model, could easily carry off more. Mexico, unlike Cuba, lacked a European parent with European allies to fear. Furthermore, the northern reaches of Mexico did not have the same dense population that Cuba did so future Mexican acquisitions could follow the Cession’s example in opening new lands for Americans and American slavery.
When Franklin Pierce replaced Millard Fillmore in the White House, he endorsed the Mexican War and staffed his administration with men of solid expansionist ideals, chief among them Mexico Gang alumni from the Polk years. Even as Pierce gave John Quitman his pep talk and blessing, he looked to continue their work against Mexico. The Democracy would not have to wait any longer.