It might seem improbable today, but in the mid-1920s, the real hotbed for the Ku Klux Klan was not the American South, but New England. In Massachusetts, Klan central was in and around Worcester, a city which was growing—and transforming—at a furious pace.

In 1920, Worcester was a bigger city than Nashville, Tenn., Dallas, and San Diego. It was an industrial powerhouse that had swelled in size from about 80,000 residents to 180,000 residents in just 30 years.

"They produced huge amounts of manufactured goods—particularly in metals," said urban historian Thomas Conroy, head of the Urban Studies department at Worcester State University. "And consequently it attracted an awful lot of immigrants."

In particular, Catholic immigrants from places like Ireland, French Canada, and Italy.

"... Which, on the one hand is wonderful," Conroy said. "And on the other hand is problematic for a Yankee host culture that really wants to see people more assimilated into an American vision that they have."

It became increasingly problematic for old guard, as these new Catholic groups settled densely in neighborhoods, building their own churches and schools, opening their own bars and restaurants.

"You have a number of immigrants that are coming in that are Catholic, that are different, that are taking jobs, that are working for cheap, that are speaking languages, that are speaking a brogue," Conroy said.

Anglo leaders and industrialists battled the rising Catholic influence by encouraging immigration from Protestant countries like Sweden and Finland, and found a partner in the rising culture war in group that was itself on the rise: the Ku Klux Klan.

"When you mention Klan today you automatically go either to the Klan you learned about in K-12 school, which is a post-Civil War Klan," Conroy said.

Known as the Second Ku Klux Klan, this secret society took on the white robes and white supremacism of its postbellum predecessor, but added religious and nationalist elements—including cross burnings. They opposed blacks, Jews, Southern European immigrants and especially Catholics. The mix of prejudice and patriotism broadened the groups appeal well beyond the confines of the American South.

"Not only [is it seen] in Worcester, it’s seen up in Maine, throughout New England, it’s in the towns," Conroy said. "It’s in Boston. [James Michael] Curley is trying to deal with it at the same time. They see themselves as somehow under siege. And that this grouping is going to—with enough people—be a place to defend themselves against a Catholic onslaught."

Through the early 1920s, KKK membership in and around Worcester was growing fast—as was its visibility. There was canvassing, recruitment events, and rallies. Skirmishes broke out in area towns.

"There are reports of cross burnings in outside towns," Conroy said. "There is actually a report of a cross burning at Clark University."

It all culminated in October of 1924, at the Cultural Fairgrounds in Worcester where as many as 15,000 gathered for an enormous KKK rally they called a "Klanvocation."

"It was definitely a show of strength," Conroy said. "It was definitely a recruiting tool. Most of these rallies at the time weren’t about demands. It was sort of about lurking."

Until then, the various Catholic groups had largely kept to themselves, but on this day banded together under the banner of the Knights of Columbus, and showed up en masse. As the rally came to a close, tensions rose then boiled over.

"And what ensues is apparently a rumble par excellence, where they’re just going at it," Conroy said.

Klansmen’s cars were stoned and burned. They were beaten in the streets. The largely Irish police force made only two arrests. The melee did little to settle the battle for the cultural future of Worcester, but it did spell the end for the Klan there, which never again resurfaced in any significant way.

By the 1940s, the Second Klan had crumbled, only to be rekindled again as the civil rights movement heated up in the 1940s and 50s.

"While I don’t think history repeats itself, there certainly are cycles and there are things you can look at from the past and there’s a certain relevance to a lot of this today," Conroy said.

Immigration, religious differences, cultural assimilation, notions of what it is to be American—they’re all issues we’re grappling with in 2016. And Conroy says that looking back can help alight a better path forward.

"I would like to think we can settle things through respectful discussion," he said. "We’re not going to always agree and that’s fine. The Republic is set up so that we don’t have to agree all the time. But it allows us to have the discussion. That’s why we should look back at these moments that remind us—we don’t want to be there. We don’t want to settle our disputes with thousand-person rumbles. There’s something uncivilized and beneath us about that."