Timeline, 1820s - 1840s

Date	Key Events from 1820 up to 1849
March 1820	The Missouri Compromise of 1820 When Missouri applies for admittance as slave state, their petition is opposed by several Northerners as technically being north of the Ohio River—the river being the legal dividing line between free territories and slave territories as defined in the Northwest Ordinance of 1787. When Southerners oppose the admittance of Maine as a free state, a compromise is reached where every territory above a line extending west from the southern boundary of Missouri—36°-30’—would be forever free. (Wagner 106)
November 1832	Nullification, States’ Rights, and Secession Compromise was again the saver of the day when South Carolina threatened to secede over a tariff they believed was oppressively high. John C. Calhoun of South Carolina introduced a novel legal concept known as nullification—a state was sovereign and could “cancel” federal laws with which it disagreed. As a sovereign state, each state is said to possess superior rights to the federal government and thus could ignore laws or leave the Union at will. When South Carolina threatened to do just that, Andrew Jackson prepared to send a military force to put down what he considered was an insurrection. Before fighting could break out, Congress adopted a compromise tariff that defused the issue—for the immediate future. (American Economy)
May 1836	The Gag Rule The House of Representatives adopts a “gag rule” that prohibits the introduction of any bill that touches upon the issue of slavery. Despite yearly attempts to repeal the rule, it will remain in force until 1844. (Bowman 16)
November 1844	James K. Polk Elected President James K. Polk is elected president and promptly confronts Great Britain over Oregon and Mexico over Texas. (Polk 1848)
January 1846	Tariff of 1846 Democratic president, Southerner, and slave owner James Polk of Tennessee successfully guides a new tariff bill through Congress that replaced an earlier tariff objected to by the South. Polk’s new tariff effectively removes federal tariffs as an issue between North and South, and within the Democratic Party. Without the tariff issue to unite them, the Democrats are slowly torn apart by the divisive issue of slavery.
May 1846 – February 1848	The War with Mexico Many future Civil War commanders, from Robert E. Lee to Ulysses S. Grant, serve in the U.S. Army and experience combat for the first time. Grant would later call the war with Mexico unjust. (Grant 1:53)
August 1846	The Wilmot Proviso Despite reassurances that the United States was not seeking new territories for the expansion of slavery, Representative David Wilmot of Pennsylvania introduces a bill that, like the Northwest Ordinance written by Thomas Jefferson in 1787, would ban slavery in any new territory acquired from Mexico. The House passes the bill but it does not make it out of the Senate. President Polk makes no effort to support the bill. He also makes to effort to legalize slavery in the territories believing it cannot survive outside of the Deep South. (Polk 2:75; Wilmot 352)
February 1848	Manifest Destiny The war with Mexico ends with the signing of the Treaty of Guadalupe Hidalgo. President Polk’s war increases the size of the United States by a third while reducing Mexico by one-half. Polk’s vision of a United States that extends unbroken from the Atlantic Ocean to the Pacific Ocean—Manifest Destiny—is realized. Remaining unsettled is the issue of slavery in the territories. (Polk, 1848)
October 1849	California California asks to be admitted to the Union as a free state. Once again, Southern states threaten secession. President Zachary Taylor—himself a slave owner—tells the South that he will personally lead the army that would quash their insurrection. (Bowman 35)