In this lesson, students analyze primary source documents in an effort to answer the central historical question: Why did the Montgomery Bus Boycott succeed? The teacher first introduces the boycott and Rosa Parks by streaming a film clip from historicalthinkingmatters.org. Students then break into 3 groups and look at a textbook account of the boycott and a timeline, making a “claim” as to why the boycott succeeded and sharing it with the whole class. The groups then corroborate with 2 more documents—a letter by Jo Ann Robinson and a memo by Bayard Rustin—and make another claim. Finally, 2 more documents—a letter by Virginia Durr and a speech by Martin Luther King, Jr.—are added to the mix, and students formulate and share a final claim. In a final class discussion, students reflect on how their claims did/did not change as they encountered more evidence.