WESTPORT — When people think of “I have a dream,” many picture the March on Washington, Bloody Sunday on the Edmund Pettus Bridge and the Montgomery Bus Boycott.

These are some the landmarks of Martin Luther King Jr.’s life that are taught in school and associated with the civil rights leader, the 50th anniversary of whose death was April 4.

But an HBO documentary, “King in the Wilderness,” released earlier this year, explores a lesser-known side of King — the work he undertook in the last three years of his life.

“The only reason to do this film is to do something new,” said Trey Ellis, a Westport resident and executive producer on the documentary. “Everything you think you know about King is wrong. By 1965, all his grand accomplishments already happened, the last three years moving on to much more universal message and thornier problems. A lot of fights of his are lost to history.”

Ellis — who screened the documentary Wednesday at the Bow Tie Ultimate Royale in Westport, hosted by the Westport Library in conjunction nwith TEAM Westport — is a novelist, essayist, screenwriter and associate professor at Columbia University. His work has appeared in the New York Times, the New Yorker, Playboy and GQ, and he co-wrote the screenplay for the Emmy-nominated 1995 film “The Tuskegee Airmen.”

“I’m mainly a screenwriter and a novelist. But I got a call out of the blue asking if I’d like to be a part of this documentary marking the 50th anniversary of King’s death that would entail me flying around the country talking to these great luminaries,” Ellis said.

Ellis became the principal interviewer on the documentary and spent the better part of six months flying around the country to speak with people like Joan Biaz, Jesse Jackson and John Lewis.

“We spoke to almost everybody who was still alive in his inner circle,” Ellis said.

The film, directed by Peter Kunhardt, intersperses interviews with seldom-seen footage of King — including shots of him among family and friends at his last birthday before his assassination. They paint an intimate portrait of a man under increasing pressure from both sides of the political spectrum.

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“King in the Wilderness” can be streamed on HBO

“I think when people see the film, they’re surprised at how funny and how charming he was. Also at how depressed he was, how the weight of the world was really on him,” Ellis said.

By the end of his career, the breadth of King’s work had spread from civil rights in the South to open housing in Chicago, opposing the Vietnam War and economic inequality. In his 1968 Poor People’s Campaign, King sought to assemble a “multiracial army of the poor” to march on Washington to demand legislation that fought poverty.

Why has much of King’s critically important late-in-life work been lost to history? Ellis weighed in.

“It’s more damning about America as a whole. It’s easy to say just a few handful of whites in the South are bad. It’s also easy to say everyone should be able to vote,” Ellis said. “For true equality, King knew you had to ask much deeper questions.”

justin.papp@scni.com; @justinjpapp1; 203-842-2586