Growing up in Southern Baptist Churches (though not, technically, in the South), I was taught that the denomination was formed during the Civil War. Because there was an actual war going on, annual conventions couldn’t meet. Also, I was told, a lot of the northern churches were mixed up in politics and had been looking for an excuse to ditch the southern churches who were more concerned with missionary work.
Later, I learned that almost every last one of those details was utterly false.
The Southern Baptist Churches split off from the nationwide Triennial Baptist Convention 15 years prior to the Civil War. The primary reason they split was that the Southern Churches were pro-slavery. They were extremely pro-slavery, arguing that God picked which people were born one race or another because he knew which ones needed to be subservient, and which needed to be in charge. Most of the people who attended Baptist churches in the North were anti-slavery, and thought that all humans, being God’s children, should be equal before the law.