When the Whig Party split over slavery in the 1850s, there was an open position for the main rival of the Democrats. The “radical” Republican Party beat out the Know Nothings to fill the void. Their mere existence led to secession and Civil War. From humble beginnings, the Republican Party became the dominant political force of the late Nineteenth Century. The “Third Party System,” ranging from 1856-1894, encompasses the Civil War, Reconstruction, and the Gilded Age.