CHARLESTON, S.C. -- About two dozen of this city's fast-food workers marched Thursday afternoon to a street corner that's home to a McDonald's, a Wendy's and a KFC. Calling for a living wage of $15, they seated themselves in the middle of a freeway entrance, backing up traffic as far as the eye could see.

Charleston police were eventually forced to pull them out of the street one by one, citing them for disorderly conduct in what were deemed "non-custodial" arrests. All told, 18 people -- most of them earning right around minimum wage -- were arrested next to the McDonald's parking lot.

"I'm just tired of seeing my family struggle," Robert Brown, a 20-year-old with short dreadlocks sprouting from his McDonald's visor, said right after a cop handed him a citation ordering him to appear in court. "I can't help them at all with what I make."

The Charleston arrests were part of Thursday's nationwide protest coordinated by Fight for $15, a union-backed campaign in which workers are demanding a $15 wage and union recognition. With the support of local labor and community groups, workers have been taking part in a series of intermittent one-day strikes in various cities over the past two years, shaming big fast-food companies like McDonald's over low pay and irregular hours.

Organizers billed Thursday's strikes and protests as an escalation of the campaign through civil disobedience. Notably, the demonstrations have spread well beyond big cities like New York and Chicago, where they were originally based. On Thursday, workers took to the streets in places like Durham, North Carolina; Tucson, Arizona; and Rochester, New York, according to news reports.

A Fight for $15 spokesperson said that roughly 500 people had been arrested in the demonstrations as of Thursday afternoon, though a portion of those appeared to be citations without arrest.

In instances that HuffPost could confirm, police arrested 47 people in Kansas City, Missouri; 27 in West Milwaukee, Wisconsin; 19 in New York City's Times Square; 30 in Detroit; 11 in San Diego; 8 in Wilkinsburg, Pennsylvania; seven in Miami; and three in Denver. Police also confirmed 19 citations in Chicago; 10 in Indianapolis; 13 in Hartford, Connecticut; and 10 in Las Vegas. In most cases, the arrests and citations came after protesters were blocking traffic.

The high-profile strikes -- which tend to draw national news coverage when they happen -- have helped progressive legislators push through minimum wage hikes on the state and local level in recent months, including a $15 wage floor that will slowly go into effect in Seattle. Even President Barack Obama has held up the protests as evidence that Congress needs to hike the federal minimum wage, which hasn't been raised since 2009. The current level of $7.25 is less than half of what the Fight for $15 campaign is calling for.

"You know what? If I were looking for a job that lets me build some security for my family, I’d join a union," Obama said Monday in a Labor Day speech. "If I were busting my butt in the service industry and wanted an honest day’s pay for an honest day’s work, I’d join a union."

While the fast-food companies themselves have generally remained quiet, critics of the campaign who sympathize with the industry have tried to dismiss the protests as stunts orchestrated by the Service Employees International Union. The union has devoted millions of dollars to the campaign in an effort to bring unionism to what's generally a union-free industry.

With some exceptions, the fast-food strikes generally haven't been large enough to shut down restaurants. In fact, it isn't always clear how many of the people participating in a protest are striking workers. In Charleston on Thursday, several workers said they had the day off and wanted to take part in the protest; others told HuffPost they were missing a scheduled shift and were formally notifying their bosses they were taking part in a protected one-day strike.

Jonathan Bennett said he was supposed to be working at Arby's on Thursday.

"If we don't do this, I don't know who will," Bennett said. "$15 could change everything."

South Carolina does not mandate a minimum wage higher than the federal level. All of the workers interviewed by HuffPost on Thursday said they made less than $8 per hour at their restaurants. That works out to a full-time salary of about $16,000 per year, which is well below the poverty level for a family of three. Most workers said they don't get a full 40 hours each week, either.

As in other towns, the Charleston protest drew in just a small fraction of the city's actual fast-food workforce. But the fact that it was happening at all in South Carolina took onlookers by surprise. The state has the third-lowest union density in the nation, with little of the organized labor infrastructure that often helps lead a wage protest.

Dave Crossley, a local who came out in support of the protest, marveled at the line of workers bottling up traffic for blocks on Spring Street, chanting for "$15 and a union."

"This sort of thing doesn't happen in Charleston," he said.