When the Civil War broke out in earnest, the United States was left to decide what to do with captured slaves from the South. Returning them to the enemy was a bad option, but keeping them under the rules of war would acknowledge the South as a separate state, which they did not recognize and President Abraham Lincoln resisted. Instead, a series of measures were taken, first to forbid the return of captured slaves to the Confederate states, and then to outlaw slavery within the United States, north and south, completely.

On this day, June 19th, in 1862, Congress passed a law abolishing slavery within the bounds of the united states. Lincoln signed it quickly thereafter. Although a number of challenges to it were raised, nobody mentioned that it seemed to be in clear violation of the Supreme Court decision in the Dred Scott case, that essentially said Congress could not regulate the slave trade.

All this was a run-up to President Lincoln’s most famous act, the signing of the Emancipation Proclamation. Lincoln wisely portrayed the decision in military terms, saying it was a necessary step for the preservation of the union. He wrote in a letter to one of his generals that for a year he did not touch the issue of slavery, and when he did, he gave the Confederacy 100 days notice, allowing them time to come back the union. He continued, “They chose to disregard it, and I made the peremptory proclamation on what appeared to me to be a military necessity. And being made, it must stand.”