This Saturday, the United States turns 250. In the grand sweep of history, 250 years is barely a moment: Rome lasted a millennium, China’s dynasties ran across thousands of years. Yet in that blink, a ragged collection of colonies became the largest and most consequential economy the world has ever seen, outpacing its competitors by miles. It wrote the rules, built the institutions and invited the world in, profiting from the architecture itself. At 250, it is worth pausing to marvel.