The All of Mexico Movement was a political movement to expand the United States to include all of Mexico. It was an expression of Manifest Destiny, but it never went into effect. In the Mexican–American War of 1846-48, the United States took by force sparsely settled territory in Mexico's north, but also invaded the densely populated Mexican heartland. After the U.S. Army took Mexico City, there was renewed enthusiasm for incorporating all of Mexico. It was fiercely opposed in the U.S. Congress, especially by U.S. Senator from South Carolina, John C. Calhoun, who strongly objected to incorporating into the U.S. a territory with a dense, nonwhite population. The Treaty of Guadalupe Hidalgo ended the aspirations of the movement by acquiring the sparsely settled region in the far north of Mexico.
Background
Before James Polk took office in 1845, the United States Congress approved the annexation of Texas. Polk wished to gain control of a portion of Texas, which had declared independence from Mexico in 1836, but was still being claimed by Mexico. This paved the way for the outbreak of the Mexican–American War onApril 24, 1846. With American success on the battlefield, by the summer of 1847 there were calls for the annexation of "All Mexico", particularly among Eastern Democrats, who argued that bringing Mexico into the Union was the best way to ensure future peace in the region.
Controversies
The proposal to annex all of Mexico was controversial. Idealistic advocates of Manifest Destiny, such as John L. O'Sullivan, had always maintained that the laws of the United States should not be imposed on people against their will. The annexation of "All Mexico" would be a violation of this principle. The annexation of all Mexico also found controversy in extending U.S. citizenship to millions of Mexicans. This debate brought to the forefront one of the contradictions of Manifest Destiny: on the one hand, while identitarian ideas inherent in Manifest Destiny suggested that Mexicans, as non-whites, would present a threat to white racial integrity and thus were not qualified to become U.S. citizens, the "mission" component of Manifest Destiny suggested that Mexicans would be improved by bringing them into American democracy. Identitarianism was used to promote Manifest Destiny, but, as in the case of Calhoun and the resistance to the "All Mexico" movement, identitarianism was also used to oppose manifest destiny. Conversely, proponents of annexation of "All Mexico" regarded it as an anti-slavery measure. Many U.S. nationals were troubled by the Catholicism of Mexico, the weakness of Republicanism there, and the threat of an upsurge of Mexican nationalism.
The controversy was eventually ended by the Mexican Cession, which added the territories of Alta California and Nuevo México to the United States, both more sparsely populated than the rest of Mexico. Like the All Oregon movement, the All Mexico movement quickly abated. Historian Frederick Merk, in Manifest Destiny and Mission in American History: A Reinterpretation, argued that the failure of the All Oregon and All Mexico movements indicates that manifest destiny had not been as popular as historians have traditionally portrayed it to have been. Merk wrote that, while belief in the beneficent mission of democracy was central to American history, aggressive "continentalism" was an aberration supported by only a minority of Americans, mostly Democrats, while it was opposed by Whigs and some Democrats. Thus the Democrats of Louisiana opposed annexation of Mexico, while those in Mississippi supported it.
