Historian Gretchen Sorin has written a fascinating new book, "Driving While Black: African American Travel and the Road to Civil Rights," that dives into the role the car played in the 20th-century African American experience. Sorin talked with Sarah about how in the Jim Crow era, when riding public transportation was often humiliating and downright dangerous for black Americans, the automobile provided a way for black families to get around with safety and dignity. She also explains how cars played an instrumental role in building the civil rights movement, and why white etiquette expert Emily Post wasn't so comfortable with the rising popularity of the automobile.