The document discusses the growing differences between the Northern and Southern states leading up to the Civil War. The North had become more industrialized and urbanized, relying on manufacturing, industry, and immigration. In contrast, the Southern economy was based almost entirely on agriculture and slave labor, with most people living on farms or plantations. These economic and demographic differences created increasing tensions between free and slave states over issues like the Missouri Compromise and the expansion of slavery into new territories, putting the Union in peril.