America is on fire, and we know how it began. On May 25, a 46-year-old black man named George Floyd died in police custody in Minneapolis, unleashing political demonstrations that have spread to at least 140 cities in the United States and continue more than two weeks later.

How it ends is an open question. The National Guard was deployed to curtail outbreaks of violence in many states and President Trump called for military intervention, inflaming an already volatile national racial climate. Yet the protests have become larger and more peaceful. (See what ‘nonlethal’ weapons can do to the body.)

Protests against racial injustice and repression have a long history in this country. Examining the government and national response during