1820 Missouri Compromise.
1846 Wilmot Proviso introduced.
1847 Wilmot Proviso defeated in Senate.
"Popular sovereignty" compromise offered.
1848 Free-Soil Party founded.
Zachary Taylor elected president.
1849 California gold rush.
1850 Taylor dies; Vice President Millard Fillmore becomes president.
Compromise of 1850 becomes law.
1852 Uncle Tom's Cabin published.
Franklin Pierce elected president.
1853 Gadsden Purchase.
1854 American (Know-Nothing) Party emerges.
Kansas-Nebraska Act.
Republican Party founded.
1856 "Bleeding Kansas."
"Sack of Lawrence."
Pottawatomie massacre.
James Buchanan elected president.
1857 Dred Scott decision.
Congress rejects Lecompton constitution.
Panic of 1857.
1858 Lincoln-Douglas debates; Douglas wins Senate seat.
1859 John Brown raids Harpers Ferry.
1860 Abraham Lincoln elected president.
South Carolina secedes from Union.
1861 Six other Lower South states secede.
Confederate States of America formed.