The revolutions that raged across Europe and the Americas over seven decades, from 1760 to 1825, created the modern world. Revolutionaries shattered empires, toppled social hierarchies, and birthed a world of republics. But old injustices lingered on and the powerful engines of revolutionary change created new and insidious forms of inequality. Through a kaleidoscope of lives both familiar and unknown—from John Adams to an ambitious French naturalist —he retells the revolutionary epic as a generational story. The first revolutionary generation, fired by radical ideas, struggled to slip the hierarchical bonds of the old order. Their failures molded a second generation, more adept at mass organizing but with an illiberal tint. The sweeping political transformations they accomplished after 1800 etched social and racial inequalities into the foundations of modern democracy.