Westward Expansion of the United States
In the summer of 1845 the editor and columnist John O’Sullivan published an article in the Democratic Review that promoted the idea of westward expansion of the United States. He created a famous term called “Manifest Destiny” suggesting that it was America’ s destiny to expand its western borders to the Pacific ocean by conquering the entire North American continent in order to bring to it American democracy and the advantages of the market. “Our manifest destiny [is] to overspread the continent allotted by Providence for the free development of our yearly multiplying millions. This we have seen done by England, our old rival and enemy; and by France”. In the American public the idea of migration beyond the Mississippi territory was met with an enthusiastic interest, than America’s population grew dramatically and additional land for settlement was required. The westward expansion, however, destroyed the political balance regarding the issue of slavery that held the nation for decades together and even dramatically intensified the conflict between the Southerners and the Northerners. By 1860 the North and the South grew to such an extent apart resulting in the inevitable secession of eleven of the fifteen slave states from the Union and creation of a new nation called the Confederate States of America. The westward expansion subsequently led to the bloodiest conflict in the young American history, the American Civil War. The aim of this paper is to examine the westward expansion and to explain how it exacerbated sectional differences in the first half of the 19th century.
To understand how the westward expansion did exacerbate the sectional differences in the first half of the 19th century, it is reasonable to begin in the year 1819. In 1819, the Missouri territory applied for admission to the United States as a slave state, which led to a political crisis because the potential admission of Missouri as a slave state would undermine the balance within the Union that incorporated eleven free states and eleven slave states. To overcome this political crisis a compromise, known as the “Missouri Compromise”, was negotiated by the influential congressman Henry Clay. The Missouri Compromise suggested that Missouri would be admitted to the Union as a slave state and simultaneously Maine as a free state, thus preserving the political balance. In addition, an imaginary line would be drawn across the Louisiana Purchase lands at 36°30` latitude, thus transforming the territory south of the line into a slave territory and the land above into “free soil”. Though averting the constitutional crisis the Missouri Compromise for the first time revealed the strong sectional differences: the increasing dependence on the slave labor of the Southerners and the opposition to the slavery in the Northern states. For the former president Thomas Jefferson the Missouri crisis consolidated the division of the American nation permanently and would make any attempt to abolish slavery from the continent in the future impossible. In a letter to a friend from April 13, 1820, Jefferson wrote: "Missouri question aroused and filled me with alarm ... I have been among the most sanguine in believing that our Union would be of long duration. I now doubt it much."
In 1824, the government of Mexico allowed American settlers to move to Texas in order to boost its economic development and population growth. However, they had to learn Spanish and convert to Catholicism, though in practice these laws were often ignored. By 1834 the American population in Texas exceeded thirty thousand, expressing their desire to join the United States as a slave state. In the same year American Texans revolted against the Mexican government under General Antonio López de Santa Anna. On March 2, 1836, Texas declared its independence from Mexico and defeated Santa Anna’s troops at the Battle of San Jacinto. The now independent Lone Star Republic urged the Jackson administration to annex its territory what proved to be a flashpoint in the sectional conflict between the free and slave states. The Northerners strictly opposed the annexation of Texas, believing that it would undermine the political balance between the South and North by enhancing the power of the slave states. The Southerners, on the other hand, supported Texas’ efforts to become the twenty-eighth state of the United States. In 1845, after more than one decade of sectional tensions, U.S. president Tyler admitted Texas as a slave state by a joint resolution of Congress that let him bypass the approval of the Senate. However, a dispute between the United States and Mexico arouse about the exact boundary between Texas and the Mexican territory. The Mexican government regarded the Nueces River as the boundary, the Polk administration the Rio Grande. On April 25, 1846, it came to a skirmish between American troops and Mexican forces in the controversial territory between the two rivers. Thereupon, James K. Polk addressed the Senate and House of Representatives with following words: “The Mexican Government … after a long-continued series of menaces, have at last invaded our territory and shed the blood of our fellow-citizens on our own soil.” On May 13, the U.S. government declared war on Mexico, thus fulfilling Polk’s expansionist vision for the United States. “While annexation did not result in the immediate disruption of the Union, it [exacerbated the sectional differences and] set in motion a series of events that ultimately led to the Civil War.”
 John O’Sullivan, “Annexation” The United States Democratic Review vol. 17, no. 85 (July-August 1845), 5.
 Jennifer D. Keene, Saul Cornell, and Edward T. O’Donnell, Visions of America: A History of the United States, vol. 1, 2nd ed., (Upper Saddle River, NJ: Prentice Hall, 2012), 318, 320, 339, 342, 369f.
 David Barton, “Application of Missouri for Admission into the Union as a State”, accessed December 06, 2012, http://memory.loc.gov/cgi-bin/ampage?collId=llsp&fileName=038/llsp038.db&recNum=570.
 Keene, Cornell, and O’Donnell, 241f.
 Phyllis Raybin Emert, “A Balancing Act“Cobblestone vol. 23, no. 1 (January 2002), 3.
 Thomas Jefferson, “Thomas Jefferson to William Short, April 13, 1820”, accessed December 06, 2012, http://hdl.loc.gov/loc.mss/mtj.mtjbib023789.
 Keene, Cornell, and O’Donnell, 326-328; Lon Strauss, “Exploration and Settlement: American Expansion into the West”, University of Kansas, 11/19/12.
 Earl M. Maltz, “The Constitution and the Annexation of Texas” Constitutional commentary vol. 23, no. 3 (December 2006), 381f, 386, 391.
 Keene, Cornell, and O’Donnell, 330.
 James K. Polk, “In Senate” The Congressional Globe, May 11, 1846, 782.
 Keene, Cornell, and O’Donnell, 330.
 Maltz, 401.