The Civil War was not the result of a debate about slavery. The slave state-free state debate dominates the narrative as the cause of the Civil War, but when examined closely, one concludes that the slave state-free state debate was the result of westward expansion. In the early and mid 1800s, the United States economy thrived. As the economy thrived, expansion to new territory seemed an exciting prospect to all Americans. When John O’Sullivan coined the term “Manifest Destiny” to describe the God-given right of American society to take over the continent from Atlantic and Pacific, it became a patriotic and guiding principle for many. Manifest Destiny helped push westward expansion, and was often cited as a reason for expanding by politicians and pioneers. In the short term, however, the patriotic and seemingly uniting principle of Manifest Destiny actually increased sectionalism and did more harm than good to the relationship between the North and the South. Leading to the debate about slave vs free state was westward expansion. Westward expansion caused the Civil War; population growth and economic opportunity drove westward expansion, leading to the tension between the North and South, and ultimately the war. In order to understand how expansion caused the Civil War, the factors that drove expansion must be examined. Expansion was driven by population growth, economic opportunities available in the West, and politicians.The population of the U.S. was doubling approximately every 20 years. That level of population growth could not have continued to be supported solely by the territory that the U.S. had prior to westward expansion. The increasing population was hungry for markets, land, and resources; a hunger indicative of events to follow. In fact, many Americans were settling in Texas to satiate that hunger.Economic opportunity drove expansion and the settling and annexation of Texas serves as an example, and how expansion increased sectional tension. American settlers came to Texas because “Cotton flourished on the fertile Texas plains, and for a time, the new Mexican authorities offered free land and something approaching local autonomy to groups of settlers from the United States. By 1830 there were some 20,000 white Americans in Texas…” Texas provided economic opportunity for slave-owning Americans because it was more territory where cotton farming could prosper, and even when Mexico outlawed slavery settlers found a way to get around it. The disregard for Mexico’s authority foreshadowed Southern attitude prior to the war: the South would not recognize the authority of anyone who opposed the institution of slavery. Settlers had already tasted the prosperity of cotton farming using slave labor; it is what made cotton farming so profitable. Why would they want to give that up? When President Tyler appointed Calhoun to annex Texas, those that opposed slavery saw it as an opportunity to enter another slave state into the Union. Southerners moved to Texas for the economic opportunity and in doing so created tension with the North. Economic opportunity did not lie solely with cotton Farming in Texas; land in Oregon and the ports in California and the Puget sound district drove westward expansion as well. Southerners saw new territories as land for agriculture, and Northerners saw them as land for Northern industry. According to Carnes and Garraty, “Eastern merchants considered the west coast harbors the keys to the trade of the Orient. That San Diego and San Francisco were Mexican and the Puget Sound district was claimed by Great Britain only heightened their desire to possess them.” They go on to say, “In dozens upon dozens of towns, societies were founded to collect information and organize groups to march to the Pacific. Land hunger (stimulated by glowing reports from the scene) was the main draw… In 1843 nearly 1,000 pioneers made the long trip.” Again, the increasing population was hungry for land. Land on the coast meant land for Northern industry, manufacturing, trade, and fishing, but it also meant land for Southern agriculture. Southern Agriculture required slave labor to maintain high profit margins, so were the new territories to be entered into the Union as free states or slave states?One might argue that the slave state versus free state debate was the cause of the Civil war, but this would be a superficial explanation. The Civil War can be further traced back to westward expansion because expansion is what caused the slave state free state debate in the first place. The population was exploding as a result of economic prosperity and immigration. The economic opportunities in the new territories were different for both North and South. The South believed that they had to have slaves to grow cotton, but many in the North did not want slavery. For many in the North, slaves were competition in the job market. This debate begun during expansion, as a result of expansion; therefore, expansion caused the Civil War.