In 1863—at the height of the Civil War—President Abraham Lincoln issued the final Emancipation Proclamation which officially freed all slaves not living in specified Union-controlled areas of the Confederacy. It also allowed Black people to enroll into the military. However, this left around one million people still enslaved. In 1865, the 13th Amendment became a part of the U.S. Constitution which officially abolished slavery—and laid the groundwork for mass incarceration.

Mass incarceration is essentially the spiritual successor to slavery. It's no coincidence that the majority of people in US prisons are people of color.