As fireworks light up the skies this Fourth of July, the United States marks its 250th birthday. For a quarter of a millennium, this experiment in liberty has endured. Yet today, many Americans look at the deep political, cultural, and ideological divisions and wonder if the nation can hold together. The temptation is to believe these fractures are unprecedented. History tells a different story. Our differences are not new, and in many ways, they have been far more dangerous than what we face now.