Correction: An earlier version of this article misstated the day that the picketing would take place. This version has been updated.

Federal contract employees at some of the nation’s best-known landmarks walked off their jobs Tuesday during a day of protests over low wages and lack of benefits.

The day-long strike was organized by a group called Good Jobs Nation on behalf of the workers who serve the food and run the cash registers at museums and offices in the heart of the federal city. Some workers said they were being paid less than the federal minimum wage of $7.25, and some said they were working in a government building despite being in the country illegally.

Protesters blocked traffic at Pennsylvania Avenue, prayed for inspiration at a civil rights exhibit at the National Museum of American History, papered the National Air and Space Museum with leaflets shaped like tiny airplanes, and rallied at noontime at Union Station. There were two arrests at the Air and Space Museum, organizers said.

“It’s important for me and all my co-workers. We’re all going through the same thing: low wages, no money,” said Antonio Venegas, 24, a $9-an-hour employee at the pita shop in the Ronald Reagan Building and International Trade Center.

Workers had banded together to advocate for higher wages and better benefits from the Obama administration, their cause bolstered by a recent study by the public-policy group Demos that found that federal contracts and concessions fund nearly 2 million private-sector jobs paying $12 an hour or less. That makes the federal government the biggest creator of low-wage jobs in the country — more than Wal-Mart and McDonald’s combined, the study found.

Nearly 100,000 of those jobs are in the Washington area, according to Good Jobs Nation. Most are janitors, clerks and landscapers. Others work in stores and restaurants in federally owned buildings. At Union Station, for example, that would include Burger King, Einstein Bros. Bagels and Sbarro, the group said. At the Reagan Building, it’s Au Bon Pain.

Good Jobs Nation said its members also include workers who sew military uniforms and drive trucks owned by shipping companies that transport Defense Department supplies from factories to ports across the country.

Members of Congress’s progressive caucus — who held a Tuesday hearing dubbed “Low-Wage Work on the Federal Dime: How Our Tax Dollars Drive Inequality” — noted the irony of such low-level contract workers eking out subsistence wages as the chief executives of contracting firms earn millions in salaries and bonuses.

“If you worked in these same federal buildings in my district, if you worked directly for those agencies, you would be paid a decent wage,” Del. Eleanor Holmes Norton (D-D.C.) said at the hearing. “But the federal government has outsourced your labor and is trying to distance itself from the responsibility of your low wages.”

Some economists argue that forcing contractors to pay higher wages could ultimately be a greater burden to taxpayers. A spokesman for the General Services Administration said the individual restaurants in the Reagan Building, for example, make their own salary and hiring decisions, although they are expected to comply with applicable federal laws.

Jonathan Ross, a custodian at the National Museum of American History, said he has been at his job for four years but cannot afford health care and makes only $9.71 an hour, despite three raises of about 10 cents each.

“It’s what we do that makes the place shine,” Ross said. “And yet, I can’t afford rent. I just had to move in with my mom. If this is what I need to do to be seen and heard, this is what I am going to do.”

Ross was striking but still lingering at his workplace, pausing with other workers for a moment of reflection and prayer before the museum’s display honoring the African American college students who helped integrate lunch counters at Woolworth’s in 1960.

He was running into his bosses around every corner, but he just ignored them.

“I love it!” Ross said. “If we can’t fight for something, we’ll fall for anything. That’s real.”

Maria Martell, 55, of Arlington County said she did not show up for her 5:30 a.m. shift at Au Bon Pain on Tuesday, even though it meant that she might lose her job. She said that with her $10-an-hour job, she has trouble paying her rent and buying medications.

“We really need help. I can’t believe this is happening in a federal building,” Martell said.

Carol Morello contributed to this report.