The overriding cause of the Civil War was the dispute over the enslavement of blacks in the South. In the 40 years before the Civil War the issue had bitterly divided the country. The South considered slavery necessary to its economy and feared that freeing the slaves would lead to violence, revolution, and social upheaval. Southerners considered slavery to be constitutionally protected, and held that the federal government had no right to interfere with slavery. In the North, however, there was a growing antislavery movement, which opposed slavery in the South and, especially, its expansion into the western territories.

UniformsUniforms of the Confederate Army.

The expansion of slavery became the center of the controversy. The South feared that with the admission of non-slave territories as states of the Union, the South's equality in the U.S. Senate would end. Long outvoted in the House of Representatives, the Southern states would lose protection for slavery in the Senate, and slavery would be threatened in the South itself. Most Northerners opposed expansion because they opposed slavery; some opposed it because they believed that slave labor would compete unfairly with free labor.

This sectional dispute came to a head following the election of Abraham Lincoln, a Republican, to the Presidency in 1860. Although the Republicans had pledged not to seek the abolition of slavery in those areas where it already existed, they did oppose its expansion. The South, therefore, saw Lincoln's election as a severe threat.

Southern states asserted the principle of state sovereignty; that is, that the states had supremacy over the federal government, and had the right to secede (withdraw) from the Union. One month after Lincoln's election, the legislature of South Carolina voted to secede. By early February, 1861, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas had taken similar steps. Early in February, delegates from these states met in Montgomery, Alabama, and formed the Confederate States of America, with Jefferson Davis as President and Alexander H. Stephens as Vice President.

The seceding states claimed the right to federal property within their borders. When President Lincoln ordered reinforcement of Fort Sumter, in the harbor of Charleston, South Carolina, the first shots of the war were fired. On April 12, 1861, Confederate batteries opened fire on Major Robert Anderson's Federal garrison. With the surrender of the fort the next day, all efforts at compromise were abandoned. Lincoln appealed for 75,000 volunteers to save the Union, and ordered a naval blockade of Southern ports. Shortly thereafter Arkansas, North Carolina, Virginia, and Tennessee joined the Confederacy, and Richmond, Virginia, was made the capital.