On March 3, 1820, the House of Representatives passed the Senate version of the bill and President James Monroe signed it four days later. The following month, former President Thomas Jefferson wrote to a friend that the “Missouri question. like a bell of fire at night, woke me up and filled me with terror. I immediately considered this to be the union`s nelle. It is indeed hushed for the moment. But this is just a respite, not a last sentence. In 1854, during the organization of the Kansas and Nebraska Territories, Senator Stephen Douglas of Illinois led the Kansas-Nebraska Act, which required settlers in each territory to decide for themselves on the issue of slavery, a principle known as popular sovereignty. The controversial law effectively nullified the Missouri Compromise by allowing slavery in the area north of latitude 36º 30`. The passage of the Kansas-Nebraska Act provoked violence between pro- and anti-slavery settlers in “Bleeding Kansas” and delayed Kansas` entry into the Union. Opposition to the law led to the creation of the Republican Party and the national notoriety of Douglas` rival from Illinois, an obscure former lawyer named Abraham Lincoln. The Missouri Territory first requested the state in 1817, and in early 1819 Congress was considering allowing laws that would empower Missouri to formulate a state constitution. On February 13, 1819, when New York Congressman James Tallmadge attempted to add an amendment to this anti-slavery legislation, an ugly and furious debate about slavery and the government`s right to limit slavery followed.

Tallmadge`s amendment prohibited the continued introduction of slaves into Missouri and provided for the emancipation of those who were already there when they were 25 years old. The change happened in the House of Representatives, controlled by the more populous North, but failed in the Senate, divided equally between free and slave states. Congress postponed without resolving the Missouri issue. In 1854, the Kansas-Nebraska Act was passed, which shared the area along the 40th parallel with Kansas to the south and Nebraska to the north, giving both territories the right to vote whether to be slaves or free. For all intents and purposes, the law effectively nullified the Missouri Compromise and the Compromise of 1850, which had attempted to regulate the spread of slavery. As a result of the new law, pro- and anti-slavery supporters tried to convince the settlers to move to Kansas to influence the vote. The New England Emigrant Aid Company, an anti-slavery group, was very successful, and a group of anti-slavery activists was formed around the city of Lawrence, Kansas. At the same time, pro-slavery settlers from Missouri began to cross the border into Kansas, some established themselves as inhabitants of the territory, others simply came to vote.

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