Fifty years ago today, federal troops escorted nine black students into Little Rock's Central High School.
It wasn't the end of racism in America. Goodness knows we're still fighting that battle. It wasn't even the end of racially motivated mob violence. But it was the end of the notion that such violence, or the white supremacist attitudes that motivated it, carried any kind of moral authority. As Eisenhower made clear (PDF) at the time, "A foundation of our American way of life is our national respect for law." Mob rule could not be, and was not, allowed to trump the rule of law.
(The Eisenhower Presidential Archives has an extensive collection of documents related to the Little Rock crisis.)