| 1619 | Slavery introduced in Jamestown. |
| 1787 | Northwest Ordinances ban slavery in new territories of the Northwest. |
| 1789 | Constitution ratified ? acknowledges the existence of slavery indirectly and appears not to give Congress the power to abolish slavery, but sets 1808 as the date when Congress may abolish the slave trade. |
| 1791 | Amendment X ratified, guaranteeing states rights. |
| 1808 | Congress abolishes the slave trade. |
| 1820 | Missouri Compromise issued ? admits Missouri as a slave state and Maine as a free state; slavery is to be banned in future states above the 36° 30í line. In the constitution written by the Missouri territory, free blacks and free mulattos are barred from the future state. |
| 1821 | Mexican Independence from Spain ? Mexico begins to invite Americans to settle Texas territory under the conditions that the settlers convert to Catholicism and observe Mexican laws, including the abolition of slavery. |
| 1830 | Mexico passes anti-colonization law to prevent Americans from further colonizing Texas. |
| 1831 | Abolitionist William Lloyd Garrison begins publishing The Liberator. |
| 1831 | Nat Turner leads an uprising of approximately 70 slaves in Southampton, Virginia ? 100 Virginia slaves are slaughtered in search of Turner; Turner is executed when found. The uprising so shakes Southern states that they pass more stringent laws related to slaves, increase censorship against abolition, and make military preparations to halt further uprisings. |
| 1832 | South Carolinaís Ordinance of Nullification ? South Carolina legislature also adopts measures to enforce this ordinance, even allowing for military preparations and secession if the Federal government resorts to force. |
| 1833 | Britain abolishes slavery in her colonies ? America is becoming increasingly isolated as a nation that allows slavery |
| 1835 | Santa Anna, President of Mexico, proclaims a unified constitution for all Mexican territories, including Texas ? North American settlers in Texas announce that they intend to secede from Mexico rather than give up their "right" to slavery, which Mexico had abolished. |
| 1836 | The Battle of the Alamo ? President Santa Anna leads a siege on the Alamo , in an attempt to defend his idea of a unitary state. Mexican soldiers overwhelm the fort, but the Texansí heroic defense of the Alamo inspires North American settlers to secede. |
| 1836 | Texans declare independence from Mexico ? they name Sam Houston commander of their army, and adopt a constitution that formally legalizes slavery in Texas. |
| 1836 | Texans defeat Mexicans and capture Santa Anna at the battle of San Jacinto. The Texans ratify their own constitution, elect Sam Houston as President, and send an envoy to Washington to demand annexation or recognition of the independent Republic of Texas. Annexation of Texas will remain a controversial issue for the next nine years, as it pits pro-slavery Southerners against anti-slavery Northerners. |
| 1840 | Whig William Henry Harrison is elected President, and John Tyler is his Vice President. |
| 1841 | William Henry Harrison dies of pneumonia after only one month in office. Vice President John Tyler becomes the first American to succeed to the presidency. |
| 1842 | Webster-Ashburton Treaty between the United States and Great Britain is signed, settling boundary disputes between the U.S. and Canada. |
| 1843 | Santa Anna, President of Mexico, warns that he would consider the American annexation of Texas as tantamount to a declaration of war against Mexico. |
| 1844 | James Polk , Democrat, defeats Whig Henry Clay for the presidency. Polk is somewhat unknown, but his aggressive expansionist views on acquiring Texas, Oregon, and California strike a receptive chord among Americans. |
| 1845 | President Polk decides to treat Texas as a state, though it is still Mexican territory under international law. He sends a detachment of the U.S. army, led by Zachary Taylor, to the southwestern border of Texas to guard against "invasion" from Mexico. |
| 1845 | The term, "Manifest Destiny" appears for the first time in the expansionist magazine the Democratic Review, in an article by the editor, John OíSullivan. |
| 1845 | Polk commissions John Slidell to negotiate with Mexico for the purchase of Texas, New Mexico, and California. |
| 1845 | Texas joins the Union as the twenty-eighth state. |
| 1845 | Potato famines in Ireland begin to force great numbers of Irish immigrants to America. The migration will continue for the next several years with about 1.5 million Irish arriving. |
| 1846 | John Slidell reports that his negotiations with Mexico have been unsuccessful. Polk orders General Taylor to move the American troops further south, to a position near the left bank of the Rio Grande River, which has always been recognized as Mexican territory. |
| 1846 | Mexican forces strike Fort Texas, a fort constructed by Taylorís men. At the request of President Polk, Congress approves a declaration of war with Mexico. This war is yet another divisive issue between the North and South. |
| 1846 | Oregon boundary dispute between U.S. and Britain is settled. |
| 1846 | Wilmot Proviso introduced in the House by David Wilmot, representative from Pennsylvania, which states that "neither slavery nor involuntary servitude shall ever exist in any part of territories that might be acquired from Mexico." This bill does not pass. |
| 1847 | Abraham Lincoln takes his seat in the House of Representatives for Illinois. |
| 1848 | The Treaty of Guadalupe Hidalgo is signed by the Senate, ending the war with Mexico. The United States gains over 500,000 square miles which include what shall become the states of California, Nevada, Utah, Arizona, New Mexico, and parts of Wyoming and Colorado. Texas is also conceded to the U.S., with its boundary at the Rio Grande. The U.S. pays $15 million. |
| 1848 | The Free Soil movement begins, opposing the spread of slavery into the new territories. |
| 1848 | Zachary Taylor, hero of the Mexican War, is elected President. Millard Fillmore is Vice President. |
| 1849 | Thoreau publishes "Civil Disobedience," an essay that grew out of his refusal to pay taxes supporting the Mexican War. |
| 1850 | President Taylor dies of cholera and vice-president Millard Fillmore assumes office. |
| 1850 | Congress adopts the Compromise of 1850, based on the five resolutions as drawn up by Henry Clay. California is admitted as a free state; the territories of New Mexico and Utah are organized without any restriction on slavery, to be decided by popular sovereignty; slave trade is abolished in the District of Columbia; a more stringent Fugitive Slave Act is issued. |
| 1851 | Uncle Tomís Cabin, by Harriet Beecher Stowe, begins to appear as a serial in the anti-slavery publication, The National Era. The complete novel is published in 1852. It will sell over one million copies within a year. It will also be adapted as a stage play and thus reach even more people. |
| 1852 | A resolution against the Fugitive Slave Act is submitted by Senator Charles Sumner. |
| 1852 | Democrat Franklin Pierce is elected President over General Winfield Scott. William R. King is Vice President. |
| 1853 | Gadsden Purchase for $10 million, Mexico agrees to cede a rectangular strip of territory along the present-day border of Arizona and New Mexico, which provides part of an ideal route for a railroad to the Pacific Ocean. |
| 1854 | The Kansas-Nebraska Act passes Congress creates two new territories with "squatter" or "popular sovereignty" concerning the question of slavery. The act effectively repeals the Missouri Compromise. Opponents to this act form the basis of the new Republican Party. The party is made up of former Whigs, anti-slavery Democrats, and Free-soilers. |
| 1854 | The "Ostend Manifesto" is drawn up by American foreign ministers in Cuba they argue that Cuba must be annexed as a slave state, and that if Spain refuses to sell the island, it should be taken by force. When the document is published in the U.S., the public reaction is negative and the proposal falls from view. |
| 1854 | The Know-Nothing Party holds its first meeting in Cincinnati. |
| 1854 | "Bleeding Kansas" small scale civil war erupts in Kansas between free-state and slave-state factions. Battles will continue until 1856 and beyond. |
| 1855 | Frederick Douglass publishes his autobiography, My Bondage and My Freedom |
| 1856 | "The Caning of Sumner" Charles Sumner, the outspoken anti-slavery senator from Massachusetts, gives a speech against the pro-slavery elements in the Senate; three days later, South Carolina representative Preston Brooks beats Sumner unconscious with a cane. |
| 1856 | Democrat James Buchanan is elected President. Republican Frémont second, sweeping the Northern states. John C. Breckenridge is Vice President. |
| 1857 | Dred Scott case in Dred Scott v. Sanford, the Supreme Court declares that the Missouri Compromise is unconstitutional. |
| 1857 | Hinton R. Helper publishes the Impending Crisis of the South he argues that slavery has impoverished Southern whites; it is banned in the South. |
| 1858 | Lincoln-Douglas debates the two candidates for representative of Illinois meet for a series of seven debates. Slavery is the main subject. |
| 1859 | John Brownís raid on Harpers Ferry Brown leads a group of whites and blacks to attack the Federal arsenal. Brown is tried for conspiracy and then hanged. |
| 1860 | Republican Abraham Lincoln elected President he wins with a clear majority of electoral votes but only a plurality of the popular votes. He defeats Breckenridge, Douglas, and Bell. Hannibal Hamlin is his vice-president. |
| 1860 | In his final message to Congress, President James Buchanan stresses that states have no legal right to secede, yet neither does the Federal Government have the basis to prevent such an action. |
| 1860 | South Carolina legislature convenes and votes to secede from the Union. Meanwhile, Congress convenes in an effort to work out some compromise; the Crittenden Compromise is proposed, which would restore the Missouri Compromise line across the continent. The compromise is ineffectual in the face of the events at hand. |
| 1861 | March 4, Abraham Lincoln inaugurated president. |
| 1861 | March 11, The Confederate States of America adopts a Constitution. The Confederacy presently includes only the seven states of the Deep South Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina and Texas. |
| 1861 | April 12, South Carolina troops fire on the Federal arsenal at Fort Sumter. The Civil War begins. The states of Virginia, North Carolina, Tennessee and Arkansas will secede from the Union in coming months. Though they are slave states, the "border states" of Delaware, Maryland, Kentucky and Missouri will remain loyal to the Union. |