Below is an article which provides an excellent overview of slavery in the United States as it relates to the Civil War.  This page by no means provides all the information of how slavery impacted the Civil War.  Explore the history, laws and issues referenced through this site and beyond to better understand the ideas of the day and motivating factors.

The first imported Africans were brought as indentured servants, not slaves. They were required, as white indentured servants were, to serve seven years. Many were brought to the British North American colonies, specifically Jamestown, Virginia in 1620. However, the slave trade did not immediately expand in North America.

Slavery in British North America
1642: Massachusetts becomes the first colony to legalize slavery.
1650: Connecticut legalizes slavery.
1661: Virginia officially recognizes slavery by statute.
1662: A Virginia statute declares that children born would have the same status as their mother.
1663: Maryland legalizes slavery.
1664: Slavery is legalized in New York and New Jersey.

The Development of Slavery
The shift from indentured servants to African slaves was prompted by a dwindling class of former servants who had worked through the terms of their indentures and thus became competitors to their former masters. These newly freed servants were rarely able to support themselves comfortably, and the tobacco industry was increasingly dominated by large planters. This caused domestic unrest culminating in Bacon's Rebellion. Eventually, chattel slavery became the norm in regions dominated by plantations.

Many slaves in British North America were owned by plantation owners who lived in Britain. The British courts had made a series of contradictory rulings on the legality of slavery[99] which encouraged several thousand slaves to flee the newly-independent United States as refugees along with the retreating British in 1783. The British courts having ruled in 1772 that such slaves could not be forcibly returned to North America (see James Somersett and Somersett's Case for a review of the Somerset Decision), the British government resettled them as free men in Sierra Leone.

Early United States law
Through the Northwest Ordinance of 1787 (also known as the Freedom Ordinance) under the Continental Congress, slavery was prohibited in the territories north of the Ohio River. In the East, though, slavery was not abolished until later. The importation of slaves into the United States was banned on January 1, 1808; but not the internal slave trade, or involvement in the international slave trade externally.

Aggregation of northern free states gave rise to one contiguous geographic area, north of the Ohio River and the old Mason-Dixon line. This separation of a free North and an enslaved South launched a massive political, cultural and economic struggle.

Refugees from slavery fled the South across the Ohio River to the North via the Underground Railroad, and their presence agitated Northerners. Midwestern state governments asserted States Rights arguments to refuse federal jurisdiction over fugitives. Some juries exercised their right of jury nullification and refused to convict those indicted under the Fugitive Slave Act of 1850.

The Dred Scott decision of 1857 asserted that one could take one's property anywhere, even if one's property was chattel and one crossed into a free territory. It also asserted that African Americans could not be citizens, as many Northern states granted blacks citizenship, who (in some states) could even vote. This was an example of Slave Power, the plantation aristocracy's attempt to control the North. This turned Northern public opinion even further against slavery. After the passage of the Kansas-Nebraska Act, armed conflict broke out in Kansas Territory, where the question of whether it would be admitted to the Union as a slave state or a free state had been left to the inhabitants. The radical abolitionist John Brown was active in the mayhem and killing in "Bleeding Kansas." Anti-slavery legislators took office under the banner of the Republican Party.

Civil War
Approximately one Southern family in four held slaves prior to war. According to the 1860 U.S. census, about 385,000 individuals (i.e. 1.4% of White Americans in the country, or 4.8% of southern whites) owned one or more slaves. However, ninety-five percent of blacks lived in the South, comprising one third of the population there as opposed to one percent of the population of the North. Consequently, fears of eventual emancipation were much greater in the South than in the North.

In the election of 1860, the Republicans swept Abraham Lincoln into the Presidency (with only 39.8% of the popular vote) and legislators into Congress. Lincoln however, did not appear on the ballots in most southern states and his election split the nation along sectional lines. After decades of controlling the Federal Government, the Southern states seceded from the U.S. (the Union) to form the Confederate States of America.

Northern leaders like Lincoln viewed the prospect of a new Southern nation, with control over the Mississippi River and the West, as unacceptable. This led to the outbreak of the Civil War, which spelled the end for chattel slavery in America. However, in August of 1862 Lincoln replied to editor Horace Greeley stating his objective was to save the Union and not to either save or destroy slavery. He went on to say that if he could save the Union without freeing a single slave, he would do it. Lincoln's Emancipation Proclamation of 1863 was a reluctant gesture, that proclaimed freedom for slaves within the Confederacy, although not those in strategically important border states or the rest of the Union. However, the proclamation made the abolition of slavery an official war goal and it was implemented as the Union captured territory from the Confederacy. Slaves in many parts of the south were freed by Union armies or when they simply left their former owners. Many joined the Union Army as workers or troops, and many more fled to Northern cities.

Legally, slaves within the United States remained enslaved until the final ratification of the Thirteenth Amendment to the Constitution on December 6, 1865 (with final recognition of the amendment on December 18), eight months after the cessation of hostilities. Only in the Border state of Kentucky did a significant slave population remain by that time.