Concise Edition: American Voices: Expansionism: The Mexican War

The Polk administration’s aggressive expansionism led to war with Mexico and political debates at home. These selections, from letters written by Secretary of State James Buchanan and Charles Sumner (a future Republican senator from Massachusetts), focus on the boundaries of Texas, the issue that sparked the war. Whose position is the more persuasive?

JAMES BUCHANAN AND CHARLES SUMNER

From Buchanan’s letter to John Slidell, November 1845: In your negotiations with Mexico, the independence of Texas must be considered a settled fact, and is not to be called in question. …

It may, however, be contended on the part of Mexico, that the Nueces and not the Rio del Norte [Rio Grande], is the true western boundary of Texas. I need not furnish you arguments to controvert this position. … The jurisdiction of Texas has been extended beyond that river [the Nueces] and … representatives from the country between it and the Del Norte have participated in the deliberations both of her Congress and her Convention. …

The case is different in regard to New Mexico. Santa Fe, its capital, was settled by the Spaniards more than two centuries ago; and that province has been ever since in their possession and that of the Republic of Mexico. The Texans never have conquered or taken possession of it. … [However,] … a great portion of New Mexico being on this side of the Rio Grande and included within the limits already claimed by Texas, it may hereafter, should it remain a Mexican province, become a subject of dispute. …

It would seem to be equally the interest of both Powers, that New Mexico should belong to the United States.

From Sumner’s letter to Robert Winthrop, October 25, 1846: By virtue of an unconstitutional Act of Congress, in conjunction with the de facto government of Texas, the latter was annexed to the United States some time in the month of December, 1845.

If we regard Texas as a province of Mexico, its boundaries must be sought in the geography of that republic. If we regard it as an independent State, they must be determined by the extent of jurisdiction which the State was able to maintain. Now it seems clear that the river Nueces was always recognized by Mexico as the western boundary; and it is undisputed that the State of Texas, since its Declaration of Independence, never exercised any jurisdiction beyond the Nueces. …

In the month of January, 1846, the President of the United States directed the troops under General Taylor … to take possession of this region [west of the Nueces River]. Here was an act of aggression. As might have been expected, it produced collision. The Mexicans, aroused in selfdefence, sought to repel the invaders. …

What was the duty of Congress in this emergency? Clearly to withhold all sanction to unjust war, — to aggression upon a neighboring Republic. …

Alas! This was not the mood of Congress. With wicked speed a bill was introduced, furnishing large and unusual supplies of men and money. … This was adopted by a vote of 123 to 67; and the bill then leaped forth, fully armed, as a measure of open and active hostility against Mexico.

SOURCES : Victoria Bissell Brown and Timothy J. Shannon, eds., Going to the Source: The Bedford Reader in American History (Boston: Bedford/St. Martin’s, 2004), 1: 260–261; Sean Wilentz, ed., Major Problems in the Early Republic, 1787–1848 (Lexington, MA: D. C. Heath, 1991), 541.