Though the Civil War itself did not begin in 1787, many events from that point lead up to it. Such events like the creation of the “Northwest Ordinance of 1787”. The Northwest Ordinance of 1787 was a system of government for the territory North of Ohio. In these territories slavery would be prohibited.
While in the south cotton was becoming very profitable after the invention of the cotton gin in 1793. The southern economy depended solely on cotton production. They needed cheap labor, which meant a lot of slaves. Northern economy was based more on industries rather than agriculture. The north industry would buy the raw cotton and turn into finished goods. So since the south was based on a plantation system while the north was focused on city life. This meant the north’s society evolved as people of different cultures and classed had to work together, while the south continued to hold on to an antiquated social order. This difference between the norths would cause problems in the future.
The Missouri Compromise passed in 1820 that passed a rule that prohibited slavery in states from the former Louisiana Purchase and Main. Leaving Missouri and west of it slave states. Which later on the Southern believed that slavery would be under attack and began to build arguments to protect it.
The Mexican War of 1845–1846 was fueled, in part, by the desire of the United States to annex Texas. President James Polk asked Congress in August 1846 for $2 million to help him negotiate peace and settle the boundary with Mexico. Polk sought the acquisition of Texas and other Mexican territories. Wilmot quickly offered his proposal, known as the Wilmot Proviso, which he attached to President Polk 's funding measure. The proviso would have prohibited slavery in the new territories acquired from Mexico, including California. The 1846 Wilmot Proviso was a bold attempt by opponents of slavery to prevent its introduction in the territories purchased