An Explorer of Black History’s Uncharted Terrain

In some ways Mr. Nelson, whose graying hair is the only thing that betrays his 59 years, has been in school ever since. An accomplished director and producer of documentaries, primarily for television — his latest film, “Freedom Riders,” makes its debut on Monday night as part of the PBS series “American Experience” — he has spent his career exploring the byways of black history and culture, and passing along the stories he finds.

“I feel like I’m trying to tell African-American audiences something they haven’t heard,” he said, “because I feel like if I tell African-American audiences something new about their history, then it’s definitely going to be new for white folks too.

“In some ways,” he continued, “I’m trying not to be that guy in ‘Tarzan’ who interprets the drums for Tarzan. I don’t want to be that person.”