HBO is known for “The Sopranos,” “Curb Your Enthusiasm,” “Entourage,” and other high-profile shows. So it was understandable that Marc Levin would be a bit taken aback when HBO executives suggested that his next project be about ... the garment industry.

But it all turned out well, because the outcome of that meeting was “Schmatta: From Rags To Riches To Rags,” a documentary that will be screened on October 8 in East Hampton and Monday, October 12 in Southampton as part of the Hamptons International Film Festival. The film will be broadcast on HBO on October 19.

“I will admit that at first I was a bit flabbergasted,” admitted “Schmatta” director Mr. Levin about the suggestion from Sheila Nevins, HBO’s executive in charge of nonfiction films. “I knew the garment industry had pretty much disappeared, so at first I didn’t get the relevance. Also, I was somewhat of a fashion illiterate. I was thrown off balance. But the more I got into it, and making family connections, I realized I very much wanted to make this documentary.”

Among the family connections that Mr. Levin, who lives in Amagansett, discovered was that his great-grandfather, Isaac Levin, an immigrant from Lithuania, invented the “adjustable dress form” while working in the garment district in New York. His grandfather, Herman Levin, owned the Acme Dress Form and Hangar Company in Brooklyn. A different kind of family connection was made while working on the project: Mr. Levin’s son, Daniel, is the director of photography on “Schmatta.”

This has been an especially busy year for Mr. Levin, who already had a busy career. He emerged as a director thanks to a 1998 feature film, “Slam,” that earned awards at both the Sundance and Cannes film festivals. Much of his career since has been devoted to documentaries and television programming.

“The Protocols of Zion” is about resurgent anti-Semitism following the 9/11 attacks. “Street Time” was a series on Showtime that starred Rob Morrow and Terrence Howard. He joined Clint Eastwood, Wim Wenders, and others as directors of episodes for a PBS series on blues that was produced by Martin Scorsese. Mr. Levin has also co-produced 10 films for “America Undercover,” an HBO series on crimes and their consequences.

Last year, he was a producer of “Cadillac Records,” the feature film about Chess Records and its blues artists that starred Beyonce Knowles and Adrian Brody. And this year, in addition to promoting “Schmatta” and escorting it through the festival circuit, he is producing with Forest Whitaker “Brick City,” a series featuring Newark Mayor Cory Booker that is being broadcast on the Sundance Channel.

After that initial meeting, “Schmatta” became a labor of love for Mr. Levin. In addition to the family connections, he grasped the implications of the garment industry’s rise and fall.

“Sheila’s instinct was, if we pull all the strands together of clothes and fashion and shopping and the decline in our economy, we can tie that to the virtual demise of the garment industry,” said Mr. Levin. “Almost everyone you talk to has a friend or relative who was touched by this industry. We wanted to make sense of the garment industry’s story as a microcosm of the American economy as one century ended and another began. The story is almost the same in other bedrock American industries—steel, cars, electronics, and textiles.”

“Schmatta” shows how the industry began in the 19th century, mostly in downtown Manhattan, fueled by the labor of immigrants. For decades, the industry clothed much of the world and virtually all of the United States. In the 1950s and ’60s, it gave birth to the fashion industry, and among those making appearances in the film are Ralph Lauren, Isaac Mizrahi, and Calvin Klein. Along the way, garment industry workers were in the forefront of the labor movements that transformed many American industries.

“We’re so bedazzled by the glitz and the glamour of what has become such a huge industry that has almost transcended music and film that we don’t really think about what’s behind the curtain—the human story of everything that has led to the beautiful clothes and the models,” Mr. Levin said of the fashion industry and its humble origins in the garment district. “Yet it’s all a mirage now because we’re busted, our economy has no clothes. The film is intended to give us some sense of how we got here.”

The documentary is a somewhat romanticized view of the industry, especially the progress made by unions in improving the lives of workers. Not portrayed is how both the unions and employers used gangsters like Dutch Schultz to either intimidate factory owners or break strikes in the 1920s. The industry was well mobbed up by the late 1950s, when Carlo Gambino, the reputed “boss of bosses,” assumed control over the garment district by appointing two of his sons to powerful positions. By the early 1990s, the garment industry in New York was grossing $2.5 billion, with a significant portion of that going into the pockets of organized crime.