In late 1846 Congressman David Wilmot submitted his “Wilmot Proviso,” banning the expansion of slavery into the territories won from Mexico. This gained northern support, passed the House with bipartisan support, but failed in the Senate. In 1848, The Free Soil party called for an end to slavery in Washington DC and on slavery’s expansion. The Compromise of 1850 tried to offer something to everyone, but only worsened the sectional crisis. Based on popular sovereignty, The New Mexico territory and Utah Territory were allowed to determine to be slave or free states, and the Kansas-Nebraska Act gave residents the ability to vote to decide whether slavery would be allowed. Also included was The Fugitive Slave Act, which authorized officials to capture and return alleged escaped slaves to their owners without trials.
I believe the Civil War was unavoidable. The tension between those who were proslavery and those who were antislavery was far too great and only growing. The westward expansion led to several debates about the fate of slavery in the West and the Missouri Compromise only increased the divide between the North and South.