The PBS documentary, which aired last fall in six weekly episodes, was released on DVD Tuesday.
"[Obama's] second campaign and his reelection was even more important," said Gates by phone from his office in Cambridge, Mass. Winning a second term showed that Americans - at least, some of them - had given their imprimatur to their first black leader.
For Gates, Obama's victory fulfills a promise, that a people who once were denied the most basic human rights could thrive in a hostile environment and eventually reach positions of power.
Yet both elections were marked by some of the most rabid racist rhetoric seen in the country since the 1960s.
"None of us could anticipate the scale and the depth of animosity heaped upon our first black president," said Gates, 63, a West Virginia native who was a teenager during the civil rights movement.
If there is one theme that persists through the six parts of Many Rivers to Cross, it's this very dialectic: As Gates documents, each historical advancement achieved by black Americans was coupled with a backlash that was often violent.
Armed slave rebellions were crushed without mercy; the progress of black and white abolitionists in the 18th and 19th centuries was met with harsh local and federal crackdowns and eventually a cataclysm in the 1860s, the Civil War, that left 620,000 dead.
Similarly, Gates' episode on the civil rights movement shows how its success in changing legislation came at the cost of police brutality and the assassinations of the Rev. Dr. Martin Luther King Jr. and Malcolm X.
Many Rivers to Cross marks a refreshing break from the run-of-the mill documentary: No airtime is given to static shots of talking heads rambling on about academic abstractions.
For Gates, the best way to study history is through stories about events and the people who shaped them.
"I went looking for the canonical stories that shaped African Americans," he said. "What are the indispensable canonical stories?" Gates and his coproducers asked 40 scholars to pick "stories they thought would work for each period."
They received "a list of thousands," Gates exclaims. "Eventually, we came up with 80, then had to cut it to 71 or 72 during filming."
Instead of interviewing experts, Gates takes his experts - historians, authors, poets, chefs, musicians - to the locations where the events they're describing happened. Segments are shot at locations from Sierra Leone to the Caribbean to Massachusetts and Florida.
The series follows not just the political life of black Americans, but the remarkable way in which they helped shape American society. Nowhere in history, Gates says on-camera, has an enslaved people so thoroughly transformed the master's culture - from its cuisine to its music, drama, and literature.
That transformation was costly. Freedom eluded black Americans not only because of racist prejudice, but also because of economic exigencies: America could not have been built without the free labor provided by slaves, Gates says in the documentary.
In one scene, he stands before the Capitol building and describes with elegant detail how slaves had to quarry, shape, carry, and install the white marble pieces that make up the dome.
For Gates, to confront the history of African Americans requires confronting, head on, what he calls "our nation's fundamental hypocrisy": that a country founded on the ideals of universal liberty and equality would quite literally never have been built - not its roads, houses, farms, bridges, and cities - without the enslavement of an entire people.
Obama's election is among the stories that conclude the sixth episode of A frican Americans: Many Rivers to Cross, but so is the story of Terrence Stevens, a paralyzed New York man with muscular dystrophy who was sentenced to 15 years to life for a nonviolent drug offense. Gates said his conviction and sentence were a travesty of justice.
"We have all these black men in prison for ridiculous sentences for drugs," he said, "while almost as many black children live in poverty as when Martin Luther King was living."
Juxtaposing Obama and Stevens' stories makes for a bittersweet ending. "We could not end on a note of false triumphalism," said Gates.
"I wanted to reflect the true temper of the times: The black middle class has quadrupled, yet there are still so many terrible things affecting the black population."