The slave population in the United States stood at four million. Ninety-five percent of blacks lived in the South, comprising one third of the population there as opposed to 1% of the population of the North. The central issue in politics in the 1850s involved the extension of slavery into the western territories, which settlers from the Northern states opposed. The Whig Party split and collapsed on the slavery issue, to be replaced in the North by the new Republican Party, which was dedicated to stopping the expansion of slavery. Republicans gained a majority in every northern state by absorbing a faction of anti-slavery Democrats, and warning that slavery was a backward system that undercut democracy and economic modernization. Numerous compromise proposals were put forward, but they all collapsed. A majority of Northern voters were committed to stopping the expansion of slavery, which they believed would ultimately end slavery. Southern voters were overwhelmingly angry that they were being treated as second-class citizens. In the election of 1860, the Republicans swept Abraham Lincoln into the Presidency (with only 39.8% of the popular vote) and his party took control with legislators into Congress. The states of the deep South, convinced that the economic power of what they called "King Cotton" would overwhelm the North and win support from Europe voted to secede from the U.S. (the Union). They formed the Confederate States of America, based on the promise of maintaining slavery. War broke out in April 1861, as both sides sought wave after wave of enthusiasm among young men volunteering to form new regiments and new armies. In the North, the main goal was to preserve the union as an expression of American nationalism.