Changing Race: Morphing Identities in History is a book about people whose seemingly permanent racial identities change. Sometimes the cause is changing racial rules: Hanni grew up in Colombia. She went to school and works in the US. She is viewed as White when she is in Colombia, but as Latina in California. Sometimes people make a racial choice: W.E.B. Du Bois had both White and Black ancestry, and he had racial options, but he chose to be Black. Sometimes an outside agency—a government, a social institution—enforces a change. In the ninth century, the Khazar Kingdom converted en masse to Judaism. None of these is an instance of racial imposture—of a person who is really X pretending to be Y. It is just how their identities worked out in fluid circumstances. Changing Race explores many such instances of racial change, for both a scholarly and a popular audience. It explains in what circumstances such changes tend to take place and explores what is the work that racial change is doing.