The Battle of Pea Ridge, Arkansas, published by Kurz and Allison, Chicago, IL, 1889. (Gilder Lehrman Collection)

The Civil War marked a defining moment in United States history. Long simmering sectional tensions reached a critical stage in 1860–1861 when eleven slaveholding states seceded and formed the Confederate States of America. Political disagreement gave way to war in April 1861, as Confederates insisted on their right to leave the Union and the loyal states refused to allow them to go. Four years of fighting claimed almost 1.5 million casualties (killed, dead from disease, wounded, or taken prisoner, and of whom at least 620,000 died) directly affected untold civilians, and freed four million enslaved African Americans.

The social and economic system based on chattel slavery that the seceding states had sought to protect lay in ruins. The inviolability of the Union, most of the loyal citizenry’s pre-eminent concern throughout the conflict, was confirmed on the battlefield. In the longer term, preservation of the Union made possible the American economic and political colossus of the next century.

Before the outbreak of war in April 1861, the American republic had survived diplomatic and military crises and internal stresses. It weathered tensions with France in the late 1790s, a second war with Britain in 1812–1815, and disputes regarding international boundaries. Political wrangling over economic issues such as the tariff, a national bank, and government-supported public works (called internal improvements in the nineteenth century) proved divisive but posed no serious threat to the integrity of the Union. Despite fissures along ethnic and class lines, the majority of Americans had much in common. They were white, Christian, spoke English, and shared a heritage forged in the crucible of the Revolutionary War.

Questions relating to the institution of slavery set the stage for secession and war. Most men and women at the time would have agreed with Abraham Lincoln’s assertion in his Second Inaugural Address that slavery “was, somehow, the cause of the war.” Alexander H. Stephens, the Confederacy’s vice president, minced no words when he proclaimed in March 1861 that slavery “was the immediate cause of the late rupture and the present revolution” to establish southern independence.[1] The framers of the United States Constitution had compromised regarding slavery, creating a democratic republic that sought to ensure its citizenry’s freedoms while also reassuring the South that individual states would have the power to maintain and regulate slavery within their boundaries. The paradox of white liberty that rested in part on a foundation of black slavery was thus imbedded in the origins of the United States.

Debates over the expansion of slavery into federal territories, which were tied to the South’s effort to maintain an equal number of free and slave states, created turmoil in national politics. The Missouri Compromise of 1820, the Wilmot Proviso of 1846 (which sought to prohibit slavery in lands acquired as a result of the Mexican-American War), the establishment of the Free Soil movement in 1848, the Compromise of 1850 (which ended parity in the Senate with California’s admission as a free state), the Kansas-Nebraska Act of 1854 (which helped foster deadly territorial violence), and the Supreme Court’s Dred Scott decision in 1857 marked mileposts along the road to sectional disruption. Outside the arena of national politics, the rise of the abolition movement, Nat Turner’s bloody slave revolt in Virginia in 1831, publication of Harriet Beecher Stowe’s anti-slavery bestseller Uncle Tom’s Cabin in 1852, and John Brown’s raid on Harpers Ferry in 1859 fed fears in the South that their slave-based social and economic systems might be in jeopardy.

As sectional divisions deepened, important institutions failed to act as stabilizing forces. Several Protestant denominations, including the Baptists and Methodists, split into northern and southern branches. The national political parties, which from the 1830s until the early 1850s had pursued compromise to maintain northern and southern wings, fractured along regional lines. The Whig Party collapsed as a national entity after the presidential election of 1852, and many northern voters came to view the Democratic Party as pro-southern. The Republican Party, which rapidly gained strength in the North following its creation in the mid-1850s, adamantly opposed extending slavery into the territories and won virtually no support in the South.

Historians have debated whether the North and South had become markedly different societies by 1860. Some portray the free-soil and free-labor North, with its burgeoning commercial and industrial interests, as an emerging capitalist giant at odds with an overwhelmingly agrarian South where most capital was invested in land and slaves. Others insist that the North and South were far more alike than different. It is clear that by the late-1850s many Americans believed there were fundamental differences between the sections and had come to distrust one another about how slavery should figure in the republic’s future.

The election of 1860 triggered the secession crisis. Although Lincoln and the victorious Republicans had promised not to interfere with slavery in states where it already existed, they firmly opposed slavery’s spread to any federal territories. Between December 1860 and February 1861, the seven Deep South states seceded to avoid what they perceived as a long-term threat to their slaveholding interests. After Confederates fired on Fort Sumter in mid-April 1861, Lincoln’s call for 75,000 volunteers to suppress the rebellion prompted four slave states of the Upper South, including Virginia, to join their Deep South brethren. Four other slave states, typically called the Border States, remained loyal to the Union.

Both sides mobilized on a scale unprecedented in American history. Drawing on an 1860 population of just more than 1,000,000 military-age white males, the Confederacy placed between 800,000 and 900,000 men in uniform (fragmentary records do not permit a precise count). The United States mustered at least 2.1 million men, about half of its 1860 military-age population. More than 180,000 African American men served in United States Army units and another 20,000 in the Navy. Apart from its much larger population, the United States held decided advantages in industrial capacity, commercial interests, and financial infrastructure.

Yet either side could have prevailed. The Confederacy sought independence and only had to defend itself. The United States sought to compel the seceded states to abandon their hopes to found a new nation. Union armies would have to invade the Confederacy, destroy its capacity to wage war, and crush the will of the southern people to resist. The Confederacy could win merely by prolonging the war to a point where the loyal citizenry considered the effort too costly in lives and money. George Wythe Randolph, who served as Confederate secretary of war, commented in 1861 that Union forces “may overrun our frontier States and plunder our coast but, as for conquering us, the thing is an impossibility.”

Union and Confederate leaders adopted very different strategies to achieve victory. Beginning in 1861 with Winfield Scott’s so-called “Anaconda Plan,” the United States pursued a strategy that included a naval blockade to restrict the flow of goods into southern ports, a combined Army-Navy effort to divide the Confederacy by seizing control of the Mississippi River, and major offensives into the Confederate hinterlands. The Confederacy first tried to defend all of its borders, but for most of the war Jefferson Davis and his advisers followed what often is termed a defensive-offensive strategy. Confederate armies generally stood on the strategic defensive, protecting as much of their territory as possible. When circumstances seemed favorable, the Confederacy launched offensives—the most important of which culminated in the Battles of Antietam and Perryville in 1862 and Gettysburg in 1863.

Military fortunes ebbed and flowed for more than three years before United States forces gained a decisive advantage. The loyal states wavered more than once in their determination, most notably after Robert E. Lee frustrated Union offensives in the spring of 1863 and the spring and early summer of 1864. A string of Union successes won by Ulysses S. Grant in the West at Forts Henry and Donelson, Shiloh, Vicksburg, and Chattanooga in 1862–1863, and by William Tecumseh Sherman at Atlanta in 1864, more than counterbalanced Lee’s successes. By the autumn of 1864, with Grant as the Union general in chief, United States armies applied pressure in Virginia, Tennessee, and the Carolinas that eventually forced a Confederate surrender in the spring of 1865.

The war touched the lives of almost every American. Women assumed larger responsibilities in the workplace. In the United States, they labored as nurses (previously a male occupation), government clerks, factory workers, members of the United States Sanitary Commission and other charitable organizations that assisted soldiers, and otherwise helped the war effort. Southern white women also worked as clerks and nurses and in factories, and thousands took responsibility for running farms, as did their northern counterparts. Although the war opened opportunities outside the household for women, its end brought a general return of old patterns of employment.

Enslaved people in the South shouldered a major part of the labor burden—as they always had—and allowed the Confederacy to put a high percentage of its military-age white men into uniform. No group was more directly affected by the outcome of the war than the four million black people who were enslaved in 1861. They emerged from the struggle with their freedom (made final by the ratification of the Thirteenth Amendment to the Constitution in December 1865), though the extent to which they would be accorded equal rights remained unresolved.

Both sides made use of recent technological advances. Railroads moved hundreds of thousands of soldiers and vast quantities of supplies, and telegraphic communication permitted both governments to coordinate military movements in widely separated areas. The conflict featured numerous applications of recent military technology, among the most important of which were the rifle musket carried by most infantrymen on both sides and ironclad warships that saw action on a broad scale.

The two national governments expanded their powers in an effort to mount sustained war efforts. Ironically, the Confederacy, a republic allegedly devoted to states’ rights, witnessed greater governmental intrusions into its citizens’ lives. Both sides enacted a series of national taxes, tampered with civil liberties, and resorted to conscription. Many of these measures, especially the drafts implemented by the Confederacy in 1862 and by the United States in 1863, provoked heated political debate and overt antiwar activities. The war produced spending on a scale dwarfing that of any earlier period. In 1860, the federal budget was $63,000,000; in 1865, United States expenditures totaled nearly $1.3 billion—a 200-fold increase that does not include the roughly $1 billion the Confederate government spent that year.

Emancipation marked the war’s most revolutionary development. Abolitionists and many Radical Republicans pressed for it from the outset, but the mass of white northerners (the free states were 98.8 percent white according to the 1860 census) always considered the conflict primarily a struggle for Union. As fighting dragged on and casualties mounted, Lincoln presented emancipation as a tool that would undermine the Confederacy. Although many Democrats remained bitter opponents, most of the loyal white citizenry eventually accepted emancipation as a tool to help win victory and restore the Union, to punish slaveholding aristocrats who had caused the war, and to prevent slavery-related issues from posing a future threat to the nation. Hundreds of thousands of enslaved people in the South did not wait for United States politicians to work out their fate, fleeing to Union military lines and thereby applying pressure for governmental action that would transform a struggle for Union into one that also would kill slavery.

The cost of the war was appalling. More American soldiers lost their lives than in all other wars combined from the colonial period through the last phase of the Vietnam War. The war brought wide-scale economic destruction to the Confederate states, which lost two-thirds of their assessed wealth (emancipated slaves accounted for much of this). In contrast, the northern economy thrived. Two numbers convey a sense of the relative economic cost: between 1860 and 1870, northern wealth increased by 50 percent; during that same decade, southern wealth decreased by 60 percent.

Americans remembered the war in different ways. Most white northerners recalled a crusade that saved the Union. Black Americans placed freedom at the center of their memories of the conflict. Many ex-Confederates celebrated their failed effort to carve out a distinct destiny. Their arguments, which included an attempt to minimize the importance of slavery as a factor during the secession crisis and the war, became part of the remarkably durable “Lost Cause” school of interpretation. By the end of the nineteenth century, a reconciliationist movement united some white northerners and southerners in a shared public memory of the war that rarely spoke of emancipation or black participation and deliberately avoided discussion of the bitter animosities that had divided North and South. For the first five decades of the twentieth century, the Lost Cause and reconciliation memories proved most dominant in American popular culture. The emancipation tradition gained impetus in the wake of the Civil Rights Movement of the 1960s, while the Lost Cause, at least in the public sphere, became far less prominent. Almost invisible was the Union cause, which largely disappeared from how Americans remembered and understood their great national trauma.