McDonald Corp.'s (MCD) - Get Report workers are not serving up happy meals. Instead they are fighting for more pay to even afford them.

On Monday, May 21, McDonald's workers from across the country stormed the new corporate headquarters in Chicago.

The protest is part of the #FightFor15 movement. Workers from fast-food joints from nationwide are demanding hourly salaries of $15 and union rights. 

Fight For 15 is a global movement that started in New York City in 2012. It released a letter to McDonald's on Monday. "And we are calling on McDonald's - the world's second-biggest private employer - to use its massive power and wealth to lift up people of color and our communities rather than keep us locked in poverty," the letter stated.

In morning trading, McDonald's was down 0.2%.