DARIEN — Labor Day arrived a little early on Wednesday, when more than 100 union protesters rallied at an Interstate 95 rest area, charging that the company with the long-term contract to operate 23 plazas throughout Connecticut is violating the terms of a monopoly that runs through 2044.

During an hour-long noontime rally, local, state and congressional leaders along with labor officials charged that Project Service LLC, is underpaying workers and preventing union representatives from lawfully meeting with workers.

Sal Luciano, president of the state AFL-CIO, told the cheering, chanting members of 32BJ SEIU that fast-food workers at McDonald’s, Subway and Dunkin’ Donuts are being underpaid by at least $3 an hour, and have no health benefits.

“They’re either supposed to get the $3 in money or benefits,” Luciano told Hearst Connecticut Media.

The union began reaching out to employees in March. “In the beginning they wouldn’t even let the union organizers on state property,” he said.

A spokeswoman for the New Haven-based Project Service, which won the 35-year contract in 2009, said that pay rates and benefits are the purview of the fast-food companies that sublet their spaces in the rest areas.

But Luciano said the company, which is currently involved in a partial sale to an Ireland-based investment group, has been very adversarial to union representatives who are allowed to meet with workers under a so-called neutrality clause in the 10-year-old contract with Project Service.

Supporters at the rally Wednesday included U.S. Rep. Jim Himes, D-Conn., Norwalk Mayor Harry Rilling, state Senate Majority Leader Bob Duff, D-Norwalk, state Rep. David Michel, D-Stamford, and state Sen. Julie Kushner, D-Danbury, a retired regional leader of the United Auto Workers.

Max Reiss, communications director for Gov. Ned Lamont, said after the protest that the governor wanted the demonstration to go ahead.

“The governor strongly supports the right for all workers to unionize, in addition to their ability to demonstrate,” Reiss said.

The rally, on a crowded sidewalk at the front of the rest area’s main entrance, occurred in an intermittent drizzle about an hour after Superior Court Judge Elizabeth Stewart rejected a request by Project Service to block the event, which Stewart said could go forward if access to the facility was not hindered.

“Justice has been served,” said Juan Hernandez, vice-president of 32BJ SEIU and head of the union in Connecticut, following the brief hearing Wednesday morning.

The rest area workers are asking for better wages, benefits, working conditions and the right to join a union. While the 23 plazas remain the property of the state Department of Transportation, Project Service is contracted to pay the state $2 million a year to operate the concessions, located along I-95, the Merritt and Wilbur Cross parkways, and I-395 in eastern Connecticut.

In addition, the company is supposed to pay the state 3 percent of gross receipts and 2 cents per gallon of fuel sold this year, according to the contract.

“The big franchise owners who run the McDonald’s and the other fast food companies don’t want the public to learn of the underpayment and mistreatment that has been happening at these service plazas for years,” Hernandez said. “These workers have the right to have their say, and we’re proud to defend that right in court today.”

Richard Buturla, a Milford lawyer who represents Project Service, argued Wednesday that the rally would block the rest area and put customers’ safety at risk.

The judge said she was satisfied with the union’s representation of the rally but stressed that it not interfere with the entrance and egress to the rest area by patrons.