Peek into Smithsonian's first-of-its-kind African American museum

The newest Smithsonian is almost finished. The National Museum of African American History and Culture will be the first to show the story of black Americans, reports CBS News correspondent Jan Crawford.

Some of the artifacts here feel almost sacred - like an actual slave cabin from a South Carolina plantation dating back to the 1800s and a segregated rail car used through 1960 that kept blacks and whites separate.

It spans 400 years of history of the African American experience. Architect David Adjaye won an international competition to design it.

New Smithsonian tells African-American story

"This is the most important demonstration of democracy in the world," Adjaye said. "It's a building that's really speaking about the struggles for freedom, the struggles for liberty, the things that are really about what America is and it's just really profoundly moving."

The exhibit features everything from the painful legacy of slavery and oppression to liberation and also celebrates cultural and artistic achievement.

Chuck Berry's Cadillac is still under wraps. The display cases have yet to be filled, but they're almost there.

Two years ago, CBS News interviewed museum director Lonnie Bunch.

"One of the things that worried me from the beginning was, could we find the artifacts that would move people?" Bunch said.

That's hasn't been a problem. For years, curators have been collecting artifacts. Curator Paul Gardullo helped find a World War II plane piloted by Tuskegee airmen - the first black Americans allowed to fly fighter planes.

"When I saw the first artifacts be displayed, I started to cry," Gardullo said. "We feel such a tremendous sense of excitement, but also a deep responsibility to this history."

It's an American experience through an African American lens.

"It's been a long time coming - this story which has this tragedy and hope should be told and it should be celebrated," Adjaye said.

Adjaye said the museum is on schedule and on track to open as planned in September. President Obama will cut the ribbon to open the space to the public.