About 400 workers at 70 New York City fast-food restaurants walked off the job on Thursday, in what could be the industry's largest strike in history. It's part of an ongoing push to win higher wages and the right to unionize for the city's 50,000-plus fast-food cashiers and burger flippers.

New York Communities for Change, the group spearheading the "Fast Food Forward" campaign, picked the date, April 4, because it is the anniversary of Martin Luther King's assassination in 1968, which occurred during a visit to Memphis in support of striking sanitation workers.

Thursday's strike was the second for New York's fast-food workers, after many walked off the job for a day in November. And the latest "strike is unlikely to be the last," says Ned Resnikoff at MSNBC, though "there are significant hurdles to overcome." A big one is the declining strength of unions, which is going to make the effort to organize workers "even more of an uphill climb," says Resnikoff.

In fact, workers behind the counters of fast-food restaurants are facing "a climate that is, in some ways, pre-1968 with regards to worker rights," Michael K. Honey, a civil rights historian, tells MSNBC. A spokesperson for Burger King, one of the chains affected, said the criticism was off the mark, since the company provides millions of entry-level jobs and pays competitively. McDonald's said its policy is that all of its employees "deserve to be treated with dignity."

There's certainly a lot at stake. "Fast food is becoming an ever-larger and more representative sector of the U.S. economy," says Josh Eidelson at Salon. And people employed in the industry have plenty of gripes, including low wages, paltry or non-existent benefits, and erratic schedules. "These are the quintessential example of the kinds of jobs that we have now," Columbia University political scientist Dorian Warren tells Salon, "and of the kind of job that we can expect in the future for the next few decades."

A central demand is to make a living wage. The workers are asking for $15 an hour, up from the minimum wage of $7.25 an hour. "Even $9 an hour, the [minimum wage] target that President Obama named and that New York will hit in three years, isn't enough to live on in New York City," says Sarah Jaffe at The Atlantic. "According to a 2010 report prepared by the Women's Center for Education and Career Advancement, the 'self-sufficiency standard' — how much it costs to live without relying on government subsidies — for a single adult living in the Bronx (the cheapest borough) was $12.56 an hour; for an adult with one child, that number jumps to $23.39 an hour."

And, says Jaffe, compounding the problem is the fact that "wages have been trending downward" across the U.S. since the Great Recession hit. "It's almost like we are coming to the rock bottom of how low wages can actually get in this country, how terrible the working conditions can be for folks," Jonathan Westin, executive director of NYCC, tells The Atlantic. "The only place to go is to claw our way back up."