Antebellum Period:Kansas-Nebraska Act (1854) and the Republican Party

Both the Kansas and the Nebraska Territories were North of the 36 30 line. When they asked for statehood, Congress repealed the 36 30 parallel, and determined that their slavery/free status would be determined by popular sovereignty (vote) in the two states. A small civil war, Bleeding Kansas, broke out in Kansas between the pro- and anti-slavery factions. Both Kansas and Nebraska ended up admitting as free states

Around this time, the Republican party was forming. Its goals were to stop the spread of slavery and to modernize the economy. They were looked upon as radicals and very left wing. The Kansas-Nebraska act propelled the Republican Party forward. The country was divided politically by region: the Democrats were largely Southern while the Republicans sided with the North.

Political Map of the Kansas-Nebraska Act (1854)
Source: www.pbs.org