Nineteenth-century America found itself in the midst of a religious upheaval. Prior to 1830, the majority of white Americans were of British heritage and Protestant in their beliefs. By 1830, however, the floodgates of immigration had been thrown wide open and tens of thousands of Irish and German immigrants made their way across the Atlantic.

More than two-thirds of these new settlers were Catholic, a situation that greatly alarmed many Protestant Americans and resulted in an increase in nativist organizations. This anti-Catholic bias lasted for decades.

For the most part, Americans were a deeply religious people. The Protestant work ethic was alive and well during the Civil War era, and it was the rare individual in either the North or the South who didn't attend church regularly. In the North, the evil inherent in slavery was a popular subject, and abolitionist preachers used the pulpit to stir up antislavery sentiment.

Southerners countered by quoting scripture they felt condoned slavery. Genesis 9:25-27, for example, was often used as justification for enslaving blacks. The passage quotes Noah, who has been angered by his son Ham, cursing all of Ham's descendants: “a slave shall he be to his brothers.”

According to the Bible, Ham fathered four sons, who gave rise to the southern tribes of the earth, including all of the people of Africa. Many Southerners also defended the institution with the argument that slavery was actually good for blacks because it enabled them to be converted to Christianity and thus go to heaven.