NEW YORK — Slavery in the United States was once a roaring success whose wounds still afflict the country today.

So says Henry Louis Gates, Jr., who examines both its success and shame in “The African Americans: Many Rivers to Cross,” his new PBS documentary series that traces 500 years of black history.

“Slavery is a perfect example of why we need limits on the more unfortunate aspects of human nature,” he says. “Slavery was capitalism gone berserk.”

The horrifically profitable practice of slavery and the brutal inhumanity of Jim Crow loom large in “The African Americans” (premiering at 8 p.m. today on WITV) which, through its six hours, performs a neat trick: Its reach extends far beyond American shores, venturing through the Caribbean region and all the way to Africa, while deftly folding this sprawl of black history into the larger American story that, too often, has kept the role of black America shunted to the margins.

Slavery, “the supreme hypocrisy,” was always an essential ingredient of the American experiment. White America always drew heavily on the labor, culture and traditions of blacks while denying them due credit in exchange, not to mention their human rights.

“The African Americans” doesn’t fall prey to white scapegoating. Africans practiced slavery long before white Europeans cashed in, and Gates journeys to Sierra Leone, where he visits with Africans whose forebears profited from it.

Gates, an author, Harvard scholar, social critic and filmmaker, is more interested in recognizing and discovering oft-neglected pieces of the American puzzle.