Sectional conflict

The Jacksonian era of optimism was clouded by the existence in the United States of a social contradiction—increasingly recognized as a social evil—that would eventually tear the nation apart: slavery. The words of the Declaration of Independence—"that all men are created equal"—were meaningless for the 1.5 million black people who were slaves. Thomas Jefferson, himself a slave-owner, recognized that the system was inhumane and wrote an attack on slavery into the Declaration, but Southern delegates to the Continental Congress forced him to remove the passage. The importation of slaves was outlawed in 1808, and many Northern states moved to abolish slavery, but the Southern economy was based on large plantations, which used slave workers to grow cotton, rice, tobacco and sugar. Still, in several Southern states, small populations of free blacks also worked as artisans or traders.

In 1820, Southern and Northern politicians disputed the question of whether

slavery would be legal in the western territories. Congress agreed on a compromise: Slavery was permitted in the new state of Missouri and the Arkansas territory, and it was barred everywhere west and north of Missouri. But the issue would not go away, some organized themselves into abolitionist societies, primarily in the North, Southern whites defended slavery with increasing ardor. The nation was also split over the issue of high tariff, which protected Northern industries but raised prices for Southern consumers.

Meanwhile, thousands of Americans had been settling in Texas, then a part of Mexico. The Texans found Mexican rule under General Santa Ana increasingly oppressive, and in 1835 they rebelled, defeated a Mexican army and set up the Independent Republic of Texas. In 1845, the United States annexed Texas, and Mexico suspended diplomatic relations. President James K. Polk ordered American troops into disputed territory on the Texas border. After a battle between Mexican and American soldiers in May 1846, Congress declared war on Mexico.

An American army landed near Vera Cruz in March 1847 and captured Mexico City in September. In return for $15 million, Mexico was forced to surrender an enormous expanse of territory—most of what is today California, Arizona, Nevada, Utah, New Mexico and Colorado.

In 1846, by settling a long-standing border dispute with British Canada, the United States had acquired clear title to the southern half of the Oregon Country—the present states of Oregon, Washington and Idaho. Thus America became a truly continental power, stretching from the Atlantic to the Pacific.

The acquisition of these new territories revived a troubling question: would newly acquired territories be open to slavery? In 1850, Congress voted another compromise: California was admitted as a free state, and the inhabitants of the Utah and New Mexico territories were allowed to decide the issue for themselves. Congress also passed the Fugitive Slave Act, which helped Southerners to recapture slaves who had escaped to the free states. Some Northern states did not enforce this law, however, and abolitionists continued to assist fleeing blacks. Harriet Beecher Stowe of Massachusetts wrote Uncle Tom's Cabin, a sentimental but powerful anti-slavery novel which converted many readers to the abolitionist cause. The issue of slavery became, in American politics, economics and cultural life, the central point of contention.

In 1854, Senator Stephen Douglas of Illinois persuaded Congress to allow the inhabitants of the Kansas and Nebraska territories to resolve the question of slavery within their own borders—which voided the Missouri Compromise of 1820. In Kansas, the result was a violent feud between pro-slavery and anti-slavery settlers. In 1857, the Supreme Court handed down the Dred Scott decision, which held that blacks had no rights as American citizens and that Congress had no authority to bar slavery in the Western territories.

In 1858, when Senator Douglas ran for reelection, he was challenged by Abraham Lincoln and the Republican party (a new anti-slavery party unrelated to Jefferson's Republican party). In a series of historic debates with Douglas, Lincoln remanded a halt to the spread of slavery. He was willing to tolerate slavery in the Southern states, but at the same time he affirmed that "this government cannot endure permanently half slave and half free."