From its introduction in 1839, photography has transformed the ways in which we see the world. Photographs capture events and also transform them; they depict reality but also tell a story. Scores of photographs have changed America and we will discuss several of them in detail. Some, such as Dorothea Lange’s Migrant Mother and Joe Rosenthal’s Flag Raising on Mt. Suribachi, will not come as a surprise. Others, including a nineteenth-century photograph of an immigrant, may open eyes anew. Examining the histories of these images, and learning how to read them, provides a deeper understanding of how photographs have shaped—and continue to shape--American society and culture.