In the fall of 1845, prior to the Mexican-American War, President James Polk attempted to use what he perceived as leverage to negotiate with the Mexican government to expand American borders.
To accomplish this goal, President Polk sent Congressman John Slidell of Louisiana, a fluent Spanish speaker, to Mexico for negotiations. See Daniel Walker Howe, What Hath God Wrought: Transformation of America, 1815-1848, 734. Prior to his leaving, President Polk advised him that the recent annexation of the Republic of Texas as American territory was nonnegotiable and that Slidell should focus his energy on negotiating the purchase of “California and/or New Mexico.” See id. At the very least, President Polk advised him, he was to get the Mexican officials to acknowledge that the Rio Grande was the southern border of the Republic of Texas and thus would become the southern border of America. See id.
President Polk sought to use Mexico’s indebtedness as leverage in the negotiations. While some may have estimated that Mexico was indebted to Americans some $8.5 million, “a mixed commission had found about $2 million” of that amount actually justified. Id. Mexico had stopped paying these debts in 1844, and Mexican officials acknowledged that they had not paid these debts. See id.
There was a distinct irony in American officials getting tough on another country for indebtedness. In the 1840s alone, several U.S. states had already defaulted on sums larger than the numbers at stake with Mexico, leaving foreign creditors frustrated and hurting America’s creditworthiness. See id.
Congressman Slidell accomplished virtually nothing during his time in Mexico City, and he wrote to President Polk: “A war would probably be the best mode of settling our affairs with Mexico.” Id. at 737 quoting John Slidell to James K. Polk, Dec. 29, 1845, quoted in David M. Pletcher, The Diplomacy of Annexation: Texas, Oregon, and the Mexican War, (Columbia, 1973), 357. Notably, a couple of decades later, Slidell would travel to France to request help on behalf of the Confederacy, which would also fail. See Daniel Walker Howe, What Hath God Wrought: Transformation of America, 1815-1848, 738.
Slidell’s attempted negotiations with Mexico illustrate the hopefulness of the Polk administration in expanding American borders without resorting to war. However, perhaps this also best reveals that President Polk was almost naive in his hopes. The Mexicans found it unthinkable that they would sell California to America, and President Polk must have known how much of a long shot this was.
Nonetheless, during this time, the expansion of America was the top priority. President Polk, and his supporters, would do anything it took to continue bringing in new territory and new resources. When one method failed, they drew up plans for the next method. With Mexico, the next method would be much more violent.