This is the fourth installment in an occasional series that will focus on slavery, the Constitution, and the ongoing debate over the meaning of the American founding.

When President Lyndon Johnson signed the Civil Rights Act of 1964, he invoked the historic struggle to make America a more equal society. The civil rights movement to which Johnson referred did not begin, however, in the twentieth or even the nineteenth century. The first civil rights activists emerged from the radical impulses of the American Revolution, and they employed the language in the Constitution to make their case in newspapers, courtrooms, and state houses for equal rights and full citizenship for Black people. Historian and Pulitzer Prize finalist Kate Masur, author of "Until Justice Be Done," tells us about the achievements and setbacks that marked the fight for civil rights in the antebellum U.S.