Slavery in the colonial history of the United States, from 1526 to 1776, developed from complex factors. Slavery was the main cause of disunion. Slavery had been a controversial issue during the framing of the Constitution but had been left unsettled.

The amount of indentured servitude dropped dramatically throughout the country. An Act Prohibiting Importation of Slaves sailed through Congress with little opposition. President Thomas Jefferson supported it, and it went into effect on January 1, 1808.

The U.S. Constitution barred the federal government from prohibiting the importation of slaves for twenty years. Various states passed bans on the international slave trade during that period; by 1808, the only state still allowing the importation of African slaves was South Carolina.

The Republican Party was determined to prevent any spread of slavery to the territories, which, after they were admitted as states, would give the North greater representation in Congress and the Electoral College. Many Southern leaders had threatened secession if the Republican candidate, Lincoln, won the 1860 election.

The election of Lincoln provoked the legislature of South Carolina to call a state convention to consider secession. Before the war, South Carolina did more than any other Southern state to advance the notion that a state had the right to nullify federal laws, and even to secede from the United States. The convention unanimously voted to secede on December 20, 1860, and adopted a secession declaration.

By early 1861, General Winfield Scott had devised the Anaconda Plan to win the war with as little bloodshed as possible. Scott argued that a Union blockade of the main ports would weaken the Confederate economy.

A pre-war February Peace Conference of 1861 met in Washington, proposing a solution similar to that of the Crittenden compromise; it was rejected by Congress. The Republicans proposed an alternative compromise to not interfere with slavery where it existed but the South regarded it as insufficient.

The primary Confederate force in the Eastern theater was the Army of Northern Virginia. The Army originated as the (Confederate) Army of the Potomac, which was organized on June 20, 1861, from all operational forces in northern Virginia.

Washington repeatedly protested France's violation of the Monroe Doctrine. Despite sympathy for the Confederacy, France's seizure of Mexico ultimately deterred it from war with the Union.

Abraham Lincoln was an American lawyer and statesman who served as the 16th president of the United States from 1861 until his assassination in 1865. Lincoln led the nation through the American Civil War and succeeded in preserving the Union, abolishing slavery, bolstering the federal government, and modernizing the U.S. economy.

On March 4, 1861, Abraham Lincoln was sworn in as president. In his inaugural address, he argued that the Constitution was a more perfect union than the earlier Articles of Confederation and Perpetual Union, that it was a binding contract, and called any secession "legally void".

The remaining eight slave states rejected pleas to join the Confederacy following a two-to-one no-vote in Virginia's First Secessionist Convention on April 4, 1861.

Virginia in particular was the site of many major and decisive battles. These battles would change the standing and historical memory of the United States. Richmond, Virginia served as the capital of the Confederate States of America for almost the whole of the American Civil War. It was a vital source of weapons and supplies for the war effort, and the terminus of five railroads.

The Battle of Fort Sumter was the bombardment of Fort Sumter near Charleston, South Carolina by the South Carolina militia. Battle of Fort Sumter was between United States (Union) and Confederate States of America Confederate States.

On April 15, 1861, Lincoln called on all the states to send forces to recapture the fort and other federal properties. The scale of the rebellion appeared to be small, so he called for only 75,000 volunteers for 90 days.

In April 1861, Lincoln announced the Union blockade of all Southern ports; commercial ships could not get insurance and regular traffic ended. The South blundered in embargoing cotton exports in 1861 before the blockade was effective; by the time they realized the mistake, it was too late.

In July 1861, a march by Union troops under the command of Maj. Gen. Irvin McDowell on the Confederate forces led by Gen. P. G. T. Beauregard near Washington was repulsed at the First Battle of Bull Run (also known as First Manassas).

As Southerners resigned their seats in the Senate and the House, Republicans were able to pass projects that had been blocked by Southern senators before the war. These included the Morrill Tariff, land grant colleges, a Homestead Act, a transcontinental railroad, the National Bank Act, the authorization of United States Notes by the Legal Tender Act of 1862, and the ending of slavery in the District of Columbia.

"Army of the Tennessee" was first used within the Union Army in March 1862, to describe Union forces perhaps more properly described as the "Army of West Tennessee"; these were the troops under the command of Maj. Gen. Ulysses S. Grant in the Union's District of West Tennessee.

In April 1862, a Union naval task force commanded by Commander David D. Porter attacked Forts Jackson and St. Philip, which guarded the river approach to New Orleans from the south. While part of the fleet bombarded the forts, other vessels forced a break in the obstructions in the river and enabled the rest of the fleet to steam upriver to the city.

The Battle of Shiloh was a major battle in the western theater of the American Civil War. The fighting was on April 6-7, 1862 in southwest Tennessee, where Union forces under Generals Albert Sidney Johnston and BGT Beauregard were against Union Army forces led by General Ulysses S. Grant.

The Army of the Cumberland was one of the principal Union armies in the Western Theater during the American Civil War. It was originally known as the Army of the Ohio. The origin of the Army of the Cumberland dates back to the creation of the Army of the Ohio in November 1861, under the command of Brig. Gen. Robert Anderson.

West Virginia separated from Virginia and was admitted to the Union on June 20, 1863.

Lincoln made Grant commander of all Union armies. Grant made his headquarters with the Army of the Potomac and put Maj. Gen. William Tecumseh Sherman in command of most of the western armies.

Several small skirmishes were fought in Florida, but no major battles. The biggest was the Battle of Olustee in early 1864.

At the beginning of 1864, Lincoln made Grant commander of all Union armies. Grant made his headquarters with the Army of the Potomac and put Maj. Gen.

In the United States, abolitionism, the movement that sought to end slavery in the country, was active from the late colonial era until the American Civil War, the end of which brought about the abolition of American slavery through the Thirteenth Amendment to the United States Constitution (ratified 1865).

On April 14, 1865, President Lincoln was shot by John Wilkes Booth, a Confederate sympathizer. Lincoln died early the next morning.

On May 4, all remaining Confederate forces in Alabama and Mississippi surrendered. President Johnson officially declared an end to the insurrection on May 9, 1865; Confederate president, Jefferson Davis, was captured the following day.

The final Confederate surrender was by the Shenandoah on November 6, 1865, bringing all hostilities of the four-year war to a close. Cherokee leader Stand Watie became the last Confederate general to surrender his forces.