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.
Named after its sponsor, Democratic representative David Wilmot of Pennsylvania, the proviso never passed both houses of Congress, but it did ignite an intense national debate over slavery that led to the creation of the antislavery Republican Party in 1854.