This essay is based on the author's presentation at FPRI's History Institute for Teachers on America in the Civil War Era, 1829-77. Slavery lasted for 250 years just in the territory of the United States, and for half a millennium in the Atlantic world. Teaching about it is therefore a huge assignment. The author cites five contexts for teaching: (1) the U.S. is a big place; (2) expansion of slavery during the 19th century; (3) racial slavery; (4) legal context; and (5) moral context. The author believes that it is necessary to measure slavery against the moral standards of the day and not 21st century sensibilities. Examining the autobiography of Frederick Douglass, Johnson challenges students to think about the causes and consequences of slavery, freedom, and moral accountability in the Civil War era and in our own time.