When Confederate forces fired on Fort Sumter in April 1861, thousands of patriotic southerners rushed to enlist for the Confederate cause. Samuel Langhorne Clemens, who grew up in the border state of Missouri in a slave-holding family, was among them. Clemens, who later achieved fame as the writer Mark Twain, served as second lieutenant in a Confederate militia, but only for two weeks, leading many to describe his loyalty to the Confederate cause...