Wondering what it means to be a Conservative

I was watching the film Amistad, and later reading up on the actual events that the conservatives were alarmed by the decision which freed the Africans.

In an excellent performance, John Qunicy Adams was portrayed by Anthony Hopkins.
Adams was one of the founders of the Whig party -- advocates of states rights. Here Adams argued for the African's freedom that even under Spanish law they were illegally seized.

Later the Whigs were split by the question of slavery. But what does it mean to say that the conservatives of 1841 were pro-slavery?

Referring to the Politically incorrect guide, it seems that Thomas Woods calls pro-slavery John C. Calhoun, a conservative. So it might be correct to say that the conservatives prior to 1860 were the pro-slavery.