In the spring of 1915, Boston roiled with protests the likes of which few had seen before: thousands of African-Americans rallying on the Common, marching on the State House, congregating at Faneuil Hall, and gathering in front of the Tremont Theatre to decry “The Birth of a Nation,’’ D.W. Griffith’s groundbreaking but racially abhorrent film about the Civil War, Reconstruction, and the rise of the Ku Klux Klan.

Led by newspaper editor and civil rights activist William Monroe Trotter, the protesters gained national attention as they mounted large-scale demonstrations, leading to more than 20 arrests, while also petitioning city and state officials in their doomed bid to have the film banned — tactics reminiscent of those used half a century later during the civil rights struggle of the 1960s.

Today, Trotter and the protests he led are largely forgotten, but the story is getting fresh treatment in “Birth of a Movement: The Battle Against America’s First Blockbuster,’’ a new documentary film by Bestor Cram and Susan Gray. Based on a book by Dick Lehr, a former Globe reporter who now teaches at Boston University, the documentary features interviews with filmmaker Spike Lee, Harvard scholar Henry Louis Gates Jr., and others to tell the dueling tales of Griffith and Trotter, who as editor of Boston’s The Guardian newspaper enjoyed a reputation rivaling that of his Harvard classmate W.E.B. Du Bois.

It premieres Monday at the Somerville Theatre before airing on PBS’s “Independent Lens’’ series Feb. 6.

“Booker T. Washington, W.E.B. Du Bois, and Trotter were the big three. Whatever happened to Trotter?’’ asked Lehr, who said he’d been unfamiliar with Trotter and the protests before writing his book “The Birth of a Movement: How Birth of a Nation Ignited the Battle for Civil Rights.’’ “These protests just didn’t seem like anything I knew about the early 1900s when it came to the civil rights movement.’’

Narrated by actor Danny Glover, the documentary uses clips from Griffith’s film, historical photographs, newspaper articles, and illustrations to describe how “Birth of a Nation,’’ with its portrayal of blacks as politically and sexually menacing, tore open the wounds of the Civil War in a cultural battle that raged across Boston.

“What Dick uncovered was a cautionary tale showing that the Hollywood blockbuster’s ability to misrepresent history would have a long tail,’’ said Cram, who founded Boston’s Northern Light Productions, which produced the film. “Here was a newspaperman trying to censor. Ultimately, he becomes a way of understanding what we now call hate speech. It hadn’t been codified that way.’’

Based on Thomas Dixon’s 1905 novel and play, “The Clansman,’’ Griffith’s film marked a dramatic break with earlier silent films. Using a host of novel techniques, Griffith told the tale of two white families against a sweeping backdrop of the Civil War and Reconstruction, where newly elected blacks move to legalize interracial marriage — a state of affairs remedied only by the heroic arrival of the KKK. Many of the film’s blacks were portrayed by white actors in blackface; in one scene a white Southern woman jumps to her death as she’s pursued by an amorous black soldier.

Among the film’s admirers was President Woodrow Wilson, a college friend of Dixon’s.

“It is like writing history with lightning,’’ Wilson reportedly said after a private screening at the White House — the first film afforded such an honor. “My only regret is that it is all so terribly true.’’

It wasn’t, of course, and Trotter, along with members of the recently formed NAACP, quickly recognized that with its technical mastery and unvarnished racism, “Birth of a Nation’’ presented a form of propaganda more virulent than any they’d encountered before.

“It was a medium on a whole different scale,’’ said Harvard historian Vincent Brown, who appears in the documentary. “It made terrorism heroic. That’s what saves the South and therefore the American nation from this travesty of Reconstruction and black political rule. It makes the disenfranchisement of black people natural, desirable, even essential to the preservation of America.’’

Trotter, who had previously led a successful effort to have Dixon’s play “The Clansman’’ shut down, petitioned Boston Mayor James Michael Curley to block the film. When that effort failed, he worked with the Boston chapter of the NAACP to rally thousands in opposition.

Amid protests that stretched from April to June, Trotter approached state lawmakers to ask that the city’s censorship laws be amended so Curley would no longer be the sole arbiter. The city eventually formed a censorship board, but the result was the same: The show would go on.

“This is the first time a big Hollywood show had shown up on the scene with millions of dollars at stake,’’ said filmmaker Gray. “Nobody was going to stop [Griffith].’’

“Birth of a Nation’’ soon opened in other cities, becoming the highest-grossing film of its day. It was met by similar protests in other communities, many of them organized by branches of the NAACP, which saw membership spike following the Boston protests.

Although Trotter, the first African-American to graduate Phi Beta Kappa from Harvard, was present at the inaugural meeting of the organization that eventually led to the foundation of NAACP, he would ultimately go it alone due to philosophical differences.

“Here was this national organization that was growing in power and prominence, and Trotter wouldn’t be a part of it,’’ said Lehr. Leading the protests “was his high-water mark in terms of influence.’’

Trotter continued his work at the Guardian, but his reputation began to fade, particularly after the death of his wife, Geraldine, in 1918. “He was never the same after her death,’’ said Lehr. “She was indispensable to him.’’

Trotter died 15 years later, possibly from suicide, after falling from his roof on his 62nd birthday.

Still, Gates says it’s hard to overstate the significance of Trotter and the Boston protests on the broader civil rights struggle. “These protests jump-started the movement,’’ said Gates, who is an executive producer of the film. “They were the kindling.’’

Malcolm Gay can be reached at malcolm.gay@globe.com. Follow him on Twitter @malcolmgay.