Leon Litwack, whose pioneering books on slavery demonstrated how Black people thought about and shaped their own liberation, even as they were constrained by racism in American society, died August 5 at his home in Berkeley, CA. He was 91.

Professor Litwack, a son of immigrants from Russia, brought an ethos of patriotic dissent to both his teaching and his scholarship at the University of California, Berkeley, The New York Times said. The historian’s job is to give voice to the marginalized and to make the well-off uncomfortable, he said.

He immersed himself in the archives to discover Black voices and their stories and show how they thought about, and struggled against, oppression. One notable fruit of that effort was Been in the Storm So Long: The Aftermath of Slavery (1979), which won both the Pulitzer Prize and the National Book Award.