A century after the artful mendacity that was Birth of a Nation and 75 years after the pro-Confederate pathos of Gone With a Wind, Hollywood is finally seeing big profits in sympathetic narratives about the black men and women who were once held as property. Steve McQueen’s 12 Years a Slave, which has grossed more than twice its reported $20 million budget, has been nominated for nine Oscars and is a favorite for Best Picture. Quentin Tarantino’s Django Unchained made $425 million worldwide and last year won two gold-plated statuettes, as did Stephen Spielberg’s Lincoln. In the history of American cinema, slavery has never been a hotter subject.

But is that an entirely good thing? In the absence of popular films about other aspects of black history, a steady diet of movies about slavery could reduce the larger subject—the long-term oppression and resistance of black Americans—to its most horrendous era. Such an unbalanced focus threatens to present slavery as the central drama of African-American history, a nightmare from which—only with the help of white abolitionists and the Union Army—they managed to awaken. The mighty effort of breaking the chains, these films conclude, enabled freedmen and women to join the great pursuit of happiness that should have been their birthright all along.

But the emancipation guaranteed by the 13th Amendment—the subject of Lincoln—only certified that no Americans would ever again be owned by others. It did nothing to dismantle the structures and attitudes of white supremacy that dominated every sphere of national life....