When I walked into the new National Museum of African American History and Culture for a preview last week, my excitement was tempered. I’d heard about the feats of engineering: rooms built around a massive a guard tower from Louisiana’s Angola Prison, a Southern Railroad train car and a Tuskegee Airman-flown plane. I’d heard about the big donationsfrom Oprah Winfrey and Michael Jordan. I’d followed the decades-long campaign for real estate and funding that were required to make this new institution a reality. But that was the story of the museum itself. I was worried that the exhibits might fall short of illustrating — panel by panel, artifact by artifact — the story of black America, which is not merely about the biggest names and the best-remembered movements. I was worried about what might have been intentionally left out or inadvertently forgotten.