Pro-slavery was an ideology that promoted the practice of slavery and defended against any interference with the system. By the 1830s, slavery was practiced mainly in the Southern United States. African American slaves were considered property. Slave owners justified them being property because slaves were black—in other words not people. Slaves were used on large plantations and small farms as the primary form of labor. 

Largely in response to the abolitionist arguments against slavery, pro-slavery advocates developed arguments to justify slavery as being a good thing. While anti-slavery groups pushed for a gradual end to slavery, and free-soilers sought to stop its expansion, abolitionists demanded an immediate end to the practice. Pro-slavery became as much anti-abolitionism as it was a defense of slavery.

Background

Slave culture 
It is sometimes hard to understand why southerners who did not own slaves would defend the practice of slavery. In the south at that time, slaves did not just work on plantations. There were over 4 million blacks were enslaved in the south and they far outnumbered white people. In cities like Charleston, South Carolina, slaves worked at various jobs such as carpenters, blacksmiths, bricklayers and street sweeper. They performed every kind of manual labor. They raised the family's children, cooked, cleaned and served the food to their masters. A visitor to Charleston commented “Charleston looks more like a Negro country than a country settled by white people”.  

Southerners feared a slave rebellion like the one on Haiti only a few decades earlier. They also feared that without slaves their economy would collapse completely. Slavery had become a subject of vital interest to everyone in the United States. In 1859, the raid on the federal arsenal at Harper's Ferry, Virginia by the abolitionist John Brown shocked the south. Had Brown succeeded, he intended to arm slaves in the south with weapons to revolt against their masters. Each new state admitted to the United States became a battle over whether it would be a free state or would allow slavery. Extremists from all sides flocked to territories to promote their own cause. Bleeding Kansas became a worst case example where the competing views broke down into outright guerrilla warfare. Political compromises were tried, such as the Missouri Compromise of 1820 and the Compromise of 1850.

Slave conditions 
Slaves were generally poorly fed and had minimal clothing and places to sleep. Household servants usually did better as they got the old clothes of their master's family and had access to better quality food. Slaves suffered from poor health in the heat and humidity of the south. Because of their poor diet and unsanitary living conditions, they frequently suffered from diseases. The rice plantations were the most deadly for slaves. They stood in water for most of the day under the hot sun. Malaria was a common disease. The mortality rate was highest among slave children. It averaged about 66 % generally and was as high as 90 % on rice plantations.

Slave women were frequently used for sex by their masters. If any refused they were physically beaten. Their racially mixed or mulatto children were considered slaves because their status followed that of the mother. All women in the south, black or white, were considered chattel or property, they belonged to the master. In 1808, the Act Prohibiting Importation of Slaves took effect. After this time slave breeding by their masters became a common way to produce slaves. There was also a demand for light-skinned, good looking young female slaves. These "fancy maids", slave women sold at auction as concubines or prostitutes, brought the highest prices.

Pro-slavery arguments 
The arguments for slavery by Southern spokesmen said that chattel slavery (slaves as property), as practiced in the South, was more humane than the system of "wage slavery" practiced in the industrialized Northern United States. George Fitzhugh, in his book published in 1857, Cannibals All!, maintained that pro-slavery held the moral high ground in the national debate over slavery. Fitzhugh maintained that because slaveholders owned their slaves they took better care of them than the northern capitalists who only "rented" their workers. In his earlier Sociology for the South he proposed that many white people should also be slaves.

Some pointed out that slave owners provided food and clothes for their slaves, something that northern employers did not do. Other arguments pointed out that in addition to the benefits slaves enjoyed under slavery that by keeping them separate, they did not mix with the white race. While this was a fear of many southerners, the argument played on the fears of northerners. The basis for this was the commonly held belief at the time that blacks were inferior to whites.

Others pointed out that a sudden end to slavery would cause economic collapse in the south. There would be no cotton, tobacco or rice industries. Also, that if all the slaves were freed it would lead to unemployment and chaos all over the United States. They claimed it would lead to uprisings much like the "Reign of Terror" during the French Revolution.  

These arguments and others were widely published in books, newspapers and pamphlets. They were carefully designed to promote and defend slavery.

References

Other websites 
 George Fitzhugh, Cannibals All!, Google Books 
 From Slavery to Freedom: The African-American Pamphlet Collection, 1824-1909

Slavery in the United States
1830s in the United States
1840s in the United States
1850s in the United States
1860s in the United States
Origins of the American Civil War