The Civil War (1861–1865) was the bloodiest war in American history. The primary cause of the war was the status of slavery in the nation and its newly acquired territories.
Southerners believed that their agricultural economy was dependent on slavery. They held that the North wanted to abolish slavery and destroy the South's economy. The South's leaders also maintained that slavery had to expand in order to survive. Therefore, they insisted that slavery be permitted to spread into new American territories in the West. The Missouri Compromise (1820) and the Compromise of 1850 dealt with the matter of slavery expansion. After 1850, however, compromise became almost impossible.
Northerners had a more diverse economy that did not rely on slaves as a workforce. By the 1830s, abolitionism began to spread in the North. Abolitionists believed that slavery was morally wrong and should be abolished. In the 1850s, a new political party, the Republicans, emerged on the national scene. This new party wanted to halt the spread of slavery into the West. Abraham Lincoln, a Republican, won the presidential election of 1860, and eleven southern states then left the Union to create a new nation.
When Southerners fired on Fort Sumter in 1861, the war began.