William G. Thomas III, The Border South

Although Brown's raid on Harper's Ferry failed, enslaved people liberated themselves during the Civil War that followed, fleeing their bondage at the first opportunity and moving toward the Union Army wherever it appeared. Because the Emancipation Proclamation did not free enslaved people in much of the Border region, the Union Army's zone of occupation became in effect a moving border between slavery and freedom, between impressment and enlistment.

There can be little doubt that secession and the Civil War was the defining feature for the Border South. The secession crisis set the Border (or Upper) South apart from the Lower South, as the latter rushed pell-mell out of the Union while the former stood longer in the Union. When the Lower South states seceded, the states along the border waited. Their waiting has sometimes been interpreted as weakness or vacillation on the issue of secession and by extension on the commitment to slavery. In Virginia especially and along the border generally, however, many politicians considered slavery safer in the Union than outside it. They saw great danger in the gamble of secession, but when Abraham Lincoln called for troops to stop the Lower South secession few were willing to countenance federal force in the South. Once the Border States began to secede, geography conspired to carve up the region further. The first few weeks of the war split the Border South into those states that could secede, such as Virginia, and those that because of federal military power either could not or would not, such as Maryland and Delaware.

Abraham Lincoln was a man of the Border South born in Kentucky, and he thought he understood the region as well as anyone. He drew heavily on his instincts and experience in the first months of the secession crisis his administration faced upon taking office. He famously observed that "to lose Kentucky is nearly the same as to lose the whole game" and considered its neutrality, if not its outright commitment to the Union, essential for both military and political reasons. Throughout the war Lincoln worked to peel off Border South Unionists and encourage them to stay in the Union. This policy was largely successful, especially in Kentucky, and Lincoln's understanding of his home region helped him prevent the secession of all the Border States.

As the war progressed the Border South became the scene of some of the most intense campaigns and the most brutal internecine fighting. Divided loyalties in Missouri contributed to reprisals and guerrilla attacks on civilians as well as soldiers, their families, and neighbors. The Union army resorted to forced removal of the entire population of four Missouri counties along the Kansas border to break up the guerrilla resistance. In Virginia and western Virginia the fighting broke out almost immediately in the spring of 1861. Along the border men joined both armies. In Missouri and Maryland, over two thirds of the white men enlisted in the Union Army, while in Kentucky the division was more even. Overall, the Upper South states weighed in heavily for the South, supplying over half of the total soldiers who fought for the Confederacy. But, along the border these same states supplied nearly as many Union soldiers, black and white.