The Battle of Fort Sumter was fought between Union and Confederate forces from April 12-14, 1861. After this battle both sides rallied tens of thousands more troops, and the American Civil War began in earnest.

The Three-Fifths compromise was a compromise reached by delegates at the 1787 Constitutional Convention regarding how slaves were to be counted for census purposes, so that would not be the best answer here. The Louisiana Purchase was the agreement that purchased a large swath of territory from France, so that would not be a good choice. The Mason Dixon Line was a surveying project in the early 19th century to demarcate the boundaries of Delaware, Pennsylvania, and Maryland, so that would not be the best choice. The Articles of Confederation outlined the first, short-lived government of the U.S., and so that would also not be the best choice. The Missouri Compromise was put forward by Henry Clay, and it was a federal statute that regulated the practice of slavery in the new western territories, so that would be the best choice.

The Civil War forced an innovation in naval warfare as both the Monitor and the newly renamed Virginia were newly ironclad. This was a large departure from previously purely wooden ships. Even though both ships were able to ship other non-ironclad ships during the battle, they themselves sustained little to no damage throughout the engagement and the naval battle was inconclusive. However, neither ship fought ever again after the battle. 

On April 9, 1865, General Robert E. Lee's Army of Northern Virginia officially surrendered to General Ulysses S. Grant's Union Army at Appomattox Court House in Virginia. Although there were other Confederate armies throughout the south, Lee's Army of Northern Virginia was the largest and best-trained force in the confederacy. Their surrender effectively ended all violence in the war and led to the subsequent surrender of all confederate forces thereafter. 

President Lincoln made several assurances that his administration would not initiate civil war. All aggressions early in the war were perpetrated by Confederate forces, finally culminating in the declaration of war after the attacks on Fort Sumter.

The widespread use of contemporary inventions such as the railroad, telegraph, mass-produced weapons, and mobilized factories are what lead to the Civil War being labeled as an "industrial war."

Sherman invaded from Chattanooga, Tennessee in May, 1964, resulting in the fall of the city on September 2. He battled Confederate General Joseph Johnston and Jon Bell Hood. After the fall of Atlanta, he began "Sherman's March to the Sea", an operation deep within enemy territory that focused on gaining supplies as they went and leaving wasteland in the army's path.