The fourth edition of Explaining the History of American Foreign Relations reconceptualizes this long-established classic to focus squarely on methods: not what we do, but how we do what we do. It presents revised, sharply focused essays on methods for researching national security, development, political economy, gender, religion, race, emotion, and nongovernmental organizations, alongside entirely new contributions on digital resources, spatial analysis, technology, materials, the natural world, the interaction of race and empire, US-Indigenous relations, ideology, and culture. The chapters are bracketed with an essay that assesses changes in the conception of US foreign relations history, and with an overview of how US foreign relations history is practiced in China. The essays, by scholars who have made a significant contribution in their areas of specialization, highlight conceptual approaches and methods that, taken together, offer an innovative and practical 'how-to' manual for both experienced scholars and newcomers to the field.