Origins of the American Civil War

Historians debating the origins of the American Civil War focus on the reasons why seven Southern states declared their secession from the United States (the Union), why they united to form the Confederate States of America (the "Confederacy"), and why the North refused to let them go. While most historians agree that conflicts over slavery caused the war, they disagree sharply regarding which kinds of conflict—ideological, economic, political, or social—were most important.

The primary catalyst for secession was slavery, especially Southern political leaders' resistance to attempts by Northern antislavery political forces to block the expansion of slavery into the western territories. Another explanation for secession, and the subsequent formation of the Confederacy, was white Southern nationalism. The primary reason for the North to reject secession was to preserve the Union, a cause based on American nationalism. Most of the debate is about the first question, as to why some southern states decided to secede.

Abraham Lincoln won the 1860 presidential election without being on the ballot in ten of the Southern states. His victory triggered declarations of secession by seven slave states of the Deep South, whose economies were all based on cotton cultivated using slave labor. They formed the Confederate States of America after Lincoln was elected, but before he took office. Nationalists (in the North and "Unionists" in the South) refused to recognize the declarations of secession. No foreign country's government ever recognized the Confederacy. The U.S. government under President James Buchanan refused to relinquish its forts that were in territory claimed by the Confederacy. The war itself began on April 12, 1861, when Confederate forces bombarded Fort Sumter, a major U.S. fortress in the harbor of Charleston, South Carolina.

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