I was writing a memo just now, I wrote an unique and I just stopped and looked at it and realized it was wrong. My whole world had been turned upside down. Then I found this explanation and all is right with the world.
Liberty Party (1840) wanted to abolish slavery; Free Soil Party (1848) wanted to keep slavery from expanding into Western territories; American Party (Know-Nothings in 1854 & 1856) wanted to reduce immigration (nativism); Constitutional Union Party (1860) wanted a compromise between the North & South.
In the 1840s and '50s, the party was in conflict over extending slavery to the Western territories. Southern Democrats insisted on protecting slavery in all the territories while many Northern Democrats resisted. The party split over the slavery issue in 1860 at its Presidential convention in Charleston, South Carolina.