Eli Blumenthal, and John Bacon

USA TODAY

NEW YORK — Demonstrators with a laundry list of grievances rallied here, teachers picketed in Philadelphia, and police in Paris fired tear gas to disperse angry political protesters Monday as May Day was marked with events around the world.

May Day, also known as International Workers' Day, annually prompts rallies highlighting workers’ rights. In the U.S., thousands of demonstrators turned out, many protesting the policies of President Trump.

In New York, chants of “Sí se puede” and “the people united will never be defeated” bellowed through Union Square Park. Demonstrators came from across the nation to protest a variety of issues ranging from the Black Lives Matter movement and refugees to climate change and the Puerto Rico debt crisis.

“We’re seeing a consistent awakening of people to the realities of the Trump administration," Bernadette Ellorin, 40, one of the event's organizers, told USA TODAY. She said Trump supporters and the mainstream media think of such efforts as "small and ineffective."

"If you study history it is these type of actions, the people marching on the streets, that actually make history," she said. "So this is our contribution toward making history, toward making change.”

Rafael Perez, 25, was among the large group supporting Puerto Rico. Perez, a grad student studying at CUNY-Hunter, is a native of the island territory. He said 1.6 million Puerto Ricans who benefit from Obamacare and Medicare won't have coverage if Congress doesn't act to protect the programs.

“It’s not only a health issue, it’s not only an economic issue, it’s a movement of the people," he said. "People are going to suffer. It’s a battle of inequality and it has to stop.”

In Oakland, four protesters were arrested while shutting down an Alameda County administration building in an act of civil disobedience, the East Bay Times reported. Several hundred people also gathered outside the San Francisco Immigration and Customs Enforcement office.

“My parents were put in concentration camps during World War II, and no one stood up for us. What’s happening now, with Trump’s immigration policies, is the same situation,” Joyce Nakamura told the Times. “I feel obligated to be here."

Organizers in Chicago estimated 20,000 people packed downtown city blocks. Many marchers held signs calling for an end to deportations, but others lobbied for workers’ rights, environmental justice and a higher minimum wage. Also seen: A handful of Trump supporters wearing baseball caps with his campaign slogan “Make America Great Again.”

In Philadelphia, the focus was more local for teachers who shut down a busy section of North Broad Street to protest the lack of a contract. About 1,000 of them skipped school, many taking personal time to highlight what they view as unfair working conditions, philly.com reported.

In France, scores of hooded youths threw firebombs at security forces as the country’s main unions drew a massive turnout for a “day of mobilization” against far-right presidential candidate Marine Le Pen, the Associated Press reported. Le Pen faces a runoff election Sunday against centrist Emmanuel Macron

About 1.5 million people rallied in Moscow, "but public order has not been violated," a city police spokesman told the state-run TASS news agency.

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In Greece, thousands rallied in Athens against austerity measures that have increased working hours, cut salaries and weakened protections for workers. Speakers called for a general strike May 17.

"We are still fighting for eight-hour shifts, we are still fighting for permanent positions," marcher Christos Zarkinos told Anadolu Agency news service.

May Day, once a salute to spring, morphed into a global observance of workers’ rights after a May 1, 1886, strike by workers in Chicago demanding an eight-hour workday.

Last week, Trump released a statement declaring May 1 “Loyalty Day” as a way to “recognize and reaffirm our allegiance to the principles” upon which America was built, calling on all government buildings to display the U.S. flag and schools to observe the holiday with ceremonies.

Igdalia Rojas, 32, took a day off from studying for finals at New York University to attend the Union Square event. Originally from California, she said she is a veteran of May Day rallies.

“We’re fighting for immigrant rights, for our community’s rights," she said. "We don’t want any more individuals to be deported. And I think we need to stop Trump from attacking our communities.”

Bacon reported from McLean, Va. Contributing: The Associated Press; Rick Jervis in Austin, Texas