In the 1850s, the major political disagreement between northern and southern states was about option A.) “slavery.”
After the Mexican-American War, which ended in February of 1848, a major conflict arose that caused conflict: a boundary was needed to define the difference between areas of slavery and antislavery. Especially regarding land from the Mexican-American War, the north and south both desired for a line to be drawn. The Treaty of Guadalupe-Hidalgo ceded 55% of Mexico’s land to the United States, most of which had an undecided sovereignty level. The Missouri Compromise came in to solve this issue, but it wasn’t long before Abraham Lincoln was elected and tipped the balance of slave states versus that of free states.