A sweeping reconsideration of the complexities of Emancipation and a biography of the nearly forgotten mid-20th-century urban planner who reshaped Boston and other cities have won this year’s Bancroft Prize, which is considered one of the most prestigious honors in the field of American history.

Lizabeth Cohen’s “Saving America’s Cities: Ed Logue and the Struggle to Renew Urban American in the Suburban Age,” published by Farrar Straus and Giroux, was cited for offering “a nuanced view of federally-funded urban redevelopment and of one of its major practitioners that goes beyond the simplicity of good and bad, heroes and villains.”

Reviewing the book last year in The New York Times Book Review, Alan Ehrenhalt praised Dr. Cohen, a professor of American Studies at Harvard, for her “incisive treatment of the entire urban-planning world in America in the last half of the 20th century,” and fair-mindedness in addressing what has become, he writes, “a highly polarized subject.”

The second winner, Joseph P. Reidy’s “Illusions of Emancipation: The Pursuit of Freedom and Equality in the Twilight of Slavery,” published by University of North Carolina Press, was cited by the prize committee for the way it builds on and departs from the huge existing literature on the subject to “deepen our understanding of the vagaries of Emancipation in the United States.”