1816 The American Colonization Society is founded. The organization continues to gain stature throughout the 1820's.

1820 The Missouri Compromise: to maintain a balance of power in the Senate Missouri is admitted as a slave state and Maine as a free state. Slavery was also prohibited in the rest of the Louisiana Purchase North of 36 30.

1831 (Jan.1) William Lloyd Garrison founds The Liberator.
(August) Nat Turner's Rebellion

1832 Garrison (with 11 others) founds the New England Anti-Slavery Society

Garrison publishes his attack on Colonization: Thoughts on African Colonization

1833 (Dec.) The American Anti-Slavery Society is formed.

1834 (Spring) Slavery Debates at Lane Seminary in Cincinnati; Theodore Weld emerges as the prominent abolitionist lecturer

1835 Angelina Grimke writes a letter to Garrison who publishes it in The Liberator

1836-1839

(May)U.S. Congress passes the Gag rule which tabled without further action all petitions on the subject of slavery. this touched off the Great Petition Drive of 1837-1839. During one session of Congress, in April 1838, there were enough signed petitions to fill a room 20 x 30 x 14 feet packed to the ceiling! John Quincy Adams fights to have the rule overturned.

1838 wins its independence. It then applies for annexation to the U.S. Benjamin Lundy sees it as evidence of the Great Slave Power Conspiracy in his book The War in Texas. Texas withdraws application for annexation in 1838.

1837 Grimke sisters conduct a lecture tour throughout New England climaxing in an appearance before the Mass. Legislature.

1838 (May) The new abolitionist facility in Philadelphia, Pennsylvania Hall, is burned down by angry mobs after audiences mixed with blacks and whites and men and women attended abolitionist meetings.

The American Anti-Slavery Society (AASS) claims 1/4 million members

1839 American Slavery As it Is is published and sold over 100,000 copies its first year.

1840 The movement splits: Garrison sticks with the AASS supporting women's rights and maintaining a radical stance while others form the American and Foreign Anti-Slavery Society. They eschew the woman question and work to build political alliances to gain power.

1841 With the death of William Henry Harrison after only 31 days in office, John Tyler of Virginia becomes president. Tyler would later support secession.

1842 John Q. Adams presents a petition from Haverville, Mass. to dissolve the Union (because of slavery) the House moves to censure him. Adams with Weld presents a marvelous defense and wins more to be suspicious of the slave power. In 1844 Adams is finally successful in overturning the Gag rule.

1844 James K. Polk of North Carolina wins the presidency. Expansionist in outlook Polk brought on the Mexican War.

1845 Texas is annexed to the U.S.

1846 U.S. goes to war with Mexico over the annexation of Texas and over Mexico's unwillingness to discuss further land purchases [manifest destiny]. U.S. wins and in the Feb. 1848 treaty gains Arizona, New Mexico, and California (for a sum of 15 million dollars).

The Great Slave Power Conspiracy theory gains ascendancy in Northern abolition and anti-slavery circles.

1848 Zachery Taylor of Virginia wins the presidency.

1850 After Taylor dies in office Millard Fillmore of New York becomes president.

Compromise of 1850. Maintained: California was to be admitted as a free state; slavery in Utah and New Mexico would be decided by popular sovereignty; slave trade is abolished in Washington D.C. (though you could still hold slaves); and the Fugitive Slave Law was strengthened. Abolitionists are outraged at that last point.

1852 Harriet Beecher Stowe's Uncle Tom's Cabin is published and sells 300,000 its first year and million copies in the U.S. by . It fuels anti-slavery sentiment in the North.

  Franklin Pierce of New Hampshire is elected president.

1854 Kansas-Nebraska Act. Repealed the Missouri Compromise and allowed the slavery issue to be decided in each territory by popular sovereignty. "Bleeding Kansas" results when anti-slavery and pro-slavery forces collide.

1856 James Buchanan of Pennsylvania is elected president.

1856 (May) Charles Sumner delivers "The Crime Against Kansas" detailing the bloody results of Stephen Douglas's popular sovereignty theme and attacking the slave power in vicious vindictive language. Six days after the speech Sumner was beaten with a cane on the floor of the Senate.

1857 The Dred Scott Decision is handed down by the Supreme Court. Scott has sued for his freedom after accompanying his "owner" on a trip through free states. The court ruled that he was neither a citizen of Missouri nor of the U.S. and so had no right to sue. Abolitionists and anti-slavery people protested the decision.

1858 The Lincoln-Douglas Debates held across the state of Illinois. Lincoln loses the election but wins national attention and articulates what will become the platform of the emerging Republican party.

1860 Abraham Lincoln of Illinois elected president.

1863 Jan. 1 The Emancipation Proclamation is formally issued freeing slaves within the Confederacy.

Additional Links:  If the event you are looking for isn't included here; do take a look at:

The National Parks Service website on Black History. this includes materials on the underground railroad as well as a timeline.
The Civil War Timeline, for an impressive reference source of materials from the the Civil War period.