His mission is to convey the rarely told story of professional basketball’s roots.

“Everybody thinks it started in 1947, with the N.B.A., and they have no idea what professional basketball was like prior to the N.B.A.” Abdul-Jabbar, a Hall of Fame center who is now an assistant coach for the Los Angeles Lakers, said during an interview at the Armory. “In that era, it was a time when sports were segregated. A lot of people I talked to, interviewing them for the documentary, didn’t even know that the N.B.A. itself was segregated for its first three years of existence.”

Abdul-Jabbar, the film’s producer, said he always wanted to make the documentary first. “But given that nobody knows the story, this story is so obscure, I had to put it in writing first,” he said, chuckling.

The Rens won the first professional basketball title in 1939, defeating the Oshkosh All-Stars at the Chicago Coliseum. Last week, the Armory served as a stand-in for the Coliseum as a handful of former college players, dressed in tight jerseys and shorts, re-created the scene, with crisp passing, two-handed set shots and almost no dribbling.

Abdul-Jabbar interviewed dozens of people for the film, including the N.B.A. legends Bill Russell, Jerry West and Julius Erving, the musicians Wynton Marsalis and will.i.am, the poet Maya Angelou, the actor Samuel L. Jackson and the director Spike Lee. He also interviewed John Wooden, his former coach at U.C.L.A., who played against the Rens; and John Isaacs, a key Rens player, who died this year at age 93.

“They called him the Boy Wonder,” said Abdul-Jabbar, who sat down with Isaacs two years ago, during the early stages of filming. “We were lucky to get that.”