In the early morning hours of April 13, 1861, after withstanding an artillery bombardment lasting more than twenty-four hours, a small garrison of U.S. troops under the command of Major Robert Anderson raised a white flag of surrender over Fort Sumter, an island fortress lying in the harbor of Charleston, South Carolina. Anderson's troops marched out of the fortress and into captivity, having just survived the first engagement of the four-year conflict known as the Civil War.

The firing on Fort Sumter sparked feelings of anger and patriotism among the people of the northern United States. Yet many Northerners had expected this bombardment, or something like it, for several months. The country was splitting into two separate nations, Union and Confederacy, North and South, over the issues of states' rights and slavery. Even as the Southern states left the Union after the election of President...