In this episode of APUSH for ALL, we trace how Manifest Destiny’s promise of continental expansion turned into a political time bomb. From Texas annexation, the Oregon Trail, and “Mr. Polk’s War” with Mexico to the Wilmot Proviso and the Compromise of 1850, we follow how every new acre raised the explosive question of slavery’s expansion. Then we move into the 1850s crisis: Kansas–Nebraska and Bleeding Kansas, Dred Scott, John Brown’s raid, and Lincoln’s rise in 1860. By the end, the West isn’t just a frontier—it’s the fuse that blows the Union apart.