Abolitionism as a principle was far more than just the wish to limit the extent of slavery. Most Northerners recognized that slavery existed in the South and the Constitution did not allow the federal government to intervene there. Most Northerners favored a policy of gradual and compensated emancipation. After 1849 abolitionists rejected this and demanded it end immediately and everywhere.
Slavery in the United States had its roots in 1619 when twenty Africans were brought by a Dutch soldier and sold to the English colony of Jamestown, Virginia as indentured servants. The transformation from indentured servitude to racial slavery happened gradually. It was not until 1661 that a reference to slavery entered into Virginia law, directed at Caucasian servants who ran away with a black servant. It was not until the Slave Codes of 1705 that the status of African Americans as slaves would be sealed. This status would last for another 160 years, until after the end of the American Civil War with the ratification of the 13th Amendment in December 1865.
A date and terms to explore to better understand the issue are 1807, the Internal Slave trade and the External Slave trade. In 1807 the external slave trade was abolished, meaning slaves were no longer allowed to be brought from Africa to the United States. Trading in Slavery from this point forward was therefore "internal" to the nation.
The Dred Scott Decision effectively limited the ultimate expansion of slavery in the U.S., however it removed any rights to citizenship for a slave. The Fugitive Slave Act was soon passed as well, once again declaring slaves as property, not people, and allowing for their return to their owners if escaped to a free state. Riding the fence, politicians crafted the Compromise of 1850, designating the lands, boundaries and process by which a territory could be a slave or a free state. Following the Compromise of 1850, Abolitionists, who had been gaining a voice through the 1830's and 1840's, tired of the compromises and demanded an immediate end to slavery. The Unitarian Church of Boston was a strong proponent of this position.
Opposition to the Abolitionist movement in the South was strong as well and based on more than one factor. The British during the early 1800's had managed to abolish slavery in their Carribean colonies through a 10 year program of compensation of the slave owners and land management. Abolitionists in the North had seen this as a model to follow for the South. Many in the South, however, saw this effort as a failure to provide for both the land owners and the Slaves, fearing bad socio-economic results if this were attempted in their situation. Citing the results in Santo Domingo as what to expect, they strongly resisted any Federal Government program to end slavery.
Another reason for the strong opposition in the South to the Abolitionist movement was the religious underpinings. The Unitarian Church in Boston was undergoing an internal doctrinal struggle, with Theodore Parker rejecting all miracles and even the divinty of Christ. The Reverend Parker was extemely influential, however, was a leader in the Abolitionist movement, had a far reaching public voice through his writing for some of the leading journals of the day and was on the staff at Harvard. Members of Parkers church, which by the 1850's numbered more than 7000, included Louisa May Alcott, William Lloyd Garrison, Julia Ward Howe, and Elizabeth Cady Stanton.
In 1848 Theodore Parker wrote a scathing essay titled "To A Southern Slaveholder". This essay was familiar to many of the Southern Clergy from a variety of denominations. Despite a multitude of other Northern pastors from several Christian denominations also preaching against slavery, the Southern clergy had determined the Abolitionist movement was sparked by Parker. This then was an issue backed by pagans in their eyes and as a result most would not entertain the notions or recommendations of the Abolitionists and threw out the baby with the bathwater.