Many of the specific controversies over slavery had to do with territorial expansion. Not all of them. The Nullification crisis was fought ostensibly over the issue of tariffs. John Brown's raid on Harper's Ferry was an explicit attempt to set up an ongoing guerrilla resistance and "slave-stealing" operation in the South.
But many of the specific controversies arose over territorial expansion, and whether slavery would be allowed in new territories. To a large extent, the national political dispute became channeled into that broad issue.
The Mexican War was one of those specific controversies. Abraham Lincoln famously opposed it. Henry David Thoreau's famous Civil Disobedience pamphlet grew out of his being jailed for not paying taxes in protest of that war. Many Northerners, by no means only abolitionists, saw the Mexican War as a Slave Power conspiracy to seize Texas and make it a new slave state.
They were not entirely wrong. The slaveowners and their representatives did hope for such an outcome.
But there was also a national security concern that also lay behind "manifest destiny", the dream to expand the borders of the United States from the Atlantic to the Pacific. And the national security concern was in part a democratic goal of expanding the democratic republic and better securing its freedoms.
John Hope Franklin and Alfred Moss, Jr., wrote in From Slavery to Freedom: A History of African-Americans (8th edition, 2003):
Shortly before the beginning of the War of 1812 the people of the West expounded the doctrine that later came to be known as Manifest Destiny. R. M. Johnson of Kentucky, for example, said that he would not die happy until all of Britain's North American possessions were incorporated into the United States. Points of view like this came to be expressed more and more by inhabitants of tne slaveholding states, though it is true that many Northerners shared the same ideas. One of the most important motives for expansionism was declared to be the extension of the area of freedom. The area of the United States must extended so as to make possible the development of a great "empire for liberty" in the New World. It was rather strange, therefore, to hear this doctrine expounded by those who held slaves and who saw little incongruity in their position as slaveholders and their pronouncements in favor of extending freedom democracy.
The extension of democracy was probably neither a primary motive of any the Southern expansionists nor even a secondary motive of many of them. Their preoccupation was with extending the area not of freedom, but of slavery. Many Southerners called for the annexation of new areas as a means of defeating politicians who were antagonistic to the rights of Southern states. Thus, Manifest testiny became a platform from which the slaveholder could plead for an extension of the institution of slavery. White Southerners, in their thinking, had excluded blacks from their religious and moral conceptions of freedom and had rolved the new notion that the enslavement of blacks was essential to the feedom of whites. Manifest Destiny, therefore, one of America's most dramatic shibboleths in the nineteenth century, contributed substantially to the extension of slavery during the generation immediately preceding the Civil War. (my emphasis)
Franklin and Moss are making some broad generalizations here to give a quick summary of the role of westward expansion in the slavery controversies. The idea "that the enslavement of blacks was essential to the freedom of whites" developed in the Lower South during the early nineteenth century and became a founding principle of the Confederate States of America. But the earlier notion that slavery would someday fade out as the allegedly "inferior" African race became civilized was still held by some slaveowners in the Upper South right up until the Civil War.
In the next post, I'll look again at the contradictory aspects of the Mexican War as viewed by Andrew Jackson.
An Index to Confederate "Heritage" Month 2006 postings is available.