- 1820: Missouri Compromise. This compromise admitted Missouri as a slave state and Maine as a free state, and it established the 36°30′ line as the dividing line between slave and free territory in the Louisiana Territory.
- 1830: Indian Removal Act. This act authorized the federal government to negotiate treaties with Native American tribes to exchange their lands in the Southeast for lands in the West.
- 1846-1848: Mexican-American War. This war resulted in the United States acquiring a vast amount of territory in the Southwest, including California, Nevada, Utah, and parts of Arizona, Colorado, New Mexico, and Wyoming.
- 1848: Treaty of Guadalupe Hidalgo. This treaty formally ended the Mexican-American War and established the Rio Grande as the border between the United States and Mexico.
- 1850: Compromise of 1850. This compromise admitted California as a free state and organized the rest of the Mexican Cession into the territories of New Mexico and Utah, with no restrictions on slavery.
- 1854: Kansas-Nebraska Act. This act repealed the Missouri Compromise and allowed the people of Kansas and Nebraska to decide for themselves whether or not to allow slavery.
- 1854-1856: Bleeding Kansas. This period of violence in Kansas occurred as pro-slavery and anti-slavery forces competed for control of the territory.
- 1857: Dred Scott v. Sandford. This Supreme Court decision ruled that African Americans were not citizens of the United States and could not sue in federal court.
- 1860: Election of Abraham Lincoln. Lincoln's election on a platform that opposed the expansion of slavery led to the secession of South Carolina and the formation of the Confederate States of America.
In my opinion, the Civil War was inevitable. The two sides were too far apart on the issue of slavery, and there was no compromise that could satisfy both sides. The South was determined to protect its way of life, and the North was determined to end slavery. Only through war could these two sides resolve their differences.