When does a country reach a tipping point—a point when the citizenry concludes that things are simply spinning out of control, and that something different is required? The question arises, obviously, as protests and looting spread across America in the wake of the brutal police killing of a black man—shocking scenes that have come atop a once-in-a-century pandemic and a Depression-like economic slide. In a moment of crisis, it’s hard to tell when such events will simply fade away in a return to the status quo, and when they will produce lasting change in political and social structures. Yet a look back at recent history suggests that it is precisely at moments like this, when shocks pile on in succession from different directions, that Americans can choose a new course.