In the middle of the 19th century, white Americans of the North and South were to reconcile fundamental differences in their approach to government, economics, society and African American slavery. The issue of slavery in the new territories was settled by the Compromise of 1850 brokered by Whig Henry Clay and Democrat Stephen Douglas; the Compromise included admission of California as a free state and the passage of the Fugitive Slave Act to make it easier for masters to reclaim runaway slaves. In 1854, the proposed Kansas-Nebraska Act abrogated the Missouri Compromise by providing that each new state of the Union would decide its stance on slavery.
By 1860, there were nearly four million slaves residing in the United States, nearly eight times as many from 1790; within the same time period, cotton production in the U.S. boomed from less than a thousand tons to nearly one million tons per year. There were some slave rebellions—including by Gabriel Prosser (1800), Denmark Vesey (1822), and Nat Turner (1831)—but they all failed and led to tighter slave oversight in the south. Abraham Lincoln with Allan Pinkerton and Major General John Alexander McClernand at the Battle of Antietam.After Abraham Lincoln won the 1860 election, eleven Southern states seceded from the union between late 1860 and 1861, establishing a new government, the Confederate States of America, on February 8, 1861. Along with the northwestern portion of Virginia, which became West Virginia, four of the five northernmost "slave states" did not secede and became known as the Border States.
American Civil WarThe Civil War began on April 12, 1861, when Confederate forces attacked a U.S. military installation at Fort Sumter in South Carolina. In response to the attack, on April 15, Lincoln called on the states to send detachments totaling 75,000 troops to recapture forts, protect the capital, and "preserve the Union", which in his view still existed intact despite the actions of the seceding states. The two armies had their first major clash at the First Battle of Bull Run, which ended in a surprising Union defeat, but, more importantly, proved to both the Union and Confederacy that the war was going be much longer and bloodier than they had originally anticipated.
The war soon divided into two theaters: Eastern and Western. In the western theater, the Union was quite successful, with major battles, such as Perryville, producing strategic Union victories and destroying major confederate operations. Anger at military conscription during the American Civil War led to the New York Draft Riots of 1863, one of the worst incidents of civil unrest in American history. The city's Irish and Excelsior brigades were among the five Union brigades with the most combat dead.In the Eastern theater, things did not start well for the Union. In the summer of 1861, General Irvin McDowell was given the task of destroying the Confederacy in one quick battle with the newly created Army of Northeastern Virginia. Union and Confederate forces engaged in combat at Manassas Junction (Bull Run), which resulted in a surprising Union defeat due in part to steadfast Confederate defense. Following McDowell's failure, Major General George B. McClellan was put in charge of the Union armies. After reorganizing the new Army of the Potomac, McClellan failed to capture the Confederate capital of Richmond, Virginia in his Peninsula Campaign and retreated after attacks from newly appointed Confederate General Robert E. Lee.
Feeling confident in his army after defeating the Union at Second Bull Run, Lee embarked on an invasion of the north that was stopped by McClellan at the bloody Battle of Antietam. Despite this, McClellan was relieved from command for refusing to pursue Lee's crippled army. The next commander, General Ambrose Burnside, suffered a humiliating defeat by Lee's smaller army at the Battle of Fredericksburg late in 1862, causing yet another change in commanders. Lee won again at the Battle of Chancellorsville in May 1863, while losing his top aide, Stonewall Jackson. But Lee pushed too hard and ignored the Union threat in the west. Lee invaded Pennsylvania in search of supplies and to cause war weariness in the North. In perhaps the turning point of the war, Lee's army was badly beaten at the Battle of Gettysburg, July 1–3, 1863, and barely made it back to Virginia.
Simultaneously on July 4, 1863, Union forces under the command of General Ulysses S. Grant gained control of the Mississippi River at the Battle of Vicksburg, thereby splitting the Confederacy. Lincoln made General Grant commander of all Union armies.
The last two years of the war was bloody for both sides, with Grant launching a war of attrition against General Lee's Army of Northern Virginia. This war of attrition was divided into three main campaigns. The first of these, the Overland Campaign forced Lee to retreat into the city of Petersburg where Grant launched his second major offensive, the Richmond-Petersburg Campaign in which he sieged Petersburg. After a near ten-month siege, Petersburg surrendered. However, the defense of Fort Gregg allowed Lee to move his army out of Petersburg. Grant pursued and launched the final, Appomattox Campaign which resulted in Lee surrendering his Army of Northern Virginia on April 9, 1865, at Appomattox Court House. Other Confederate armies followed suit and the war ended.
Based on 1860 census figures, about 8% of all white males aged 13 to 43 died in the war, including about 6% in the North and approximately 18% in the South, establishing the American Civil War as the deadliest war in American history. Its legacy includes ending slavery in the United States, restoring the Union, and strengthening the role of the federal government. The social, political, economic and racial issues of the war decisively shaped the Reconstruction era, which lasted through 1877, and brought about changes that would eventually help make the country a united superpower.