Last year, labor officials remembered Thomas by planting a weeping cherry tree.
Perkins said then that Thomas was a pipe fitter at Mack Trucks in 1988 when he was crushed by a machine.
Mason said at least 15 people, on average, are killed while working each day across the country.
While reading a brief history of Workers Memorial Day, Jon Rosenberger, a member of the International Brotherhood of Electrical Workers, said unions have fought to save hundreds of thousands of employees' lives.
"We do mourn for the dead," Perkins said, "but the most important thing we can continue to do is fight for the living."
Del. John P. Donoghue, D-Washington, presented a proclamation in honor of the day.
Donoghue also blasted Del. Christopher B. Shank, R-Washington, for opposing a proposal to allow speed cameras in school and work zones.
Shank has said he considers the cameras an invasion of privacy that keep people from facing their accuser.
But Donoghue told union officials on Tuesday that cameras could help protect someone working on a road crew, who might be killed by a driver speeding in a sport-utility vehicle while talking on a cell phone.
Or a driver near a school might wipe out a crossing guard and five or six children, he said.
Shank "says the vote Sen. (Donald F.) Munson and I took is un-American," Donoghue said. "I don't know about you folks, but I think I did the right thing. I think Sen. Munson did the right thing."
Hagerstown Mayor Robert E. Bruchey II, a Republican, said he agreed with Donoghue and Munson on speed cameras. The best outcome would be no one getting a speeding ticket because everyone slowed down, Bruchey said.
Bruchey, who also presented a proclamation for Workers Memorial Day, said city officials are responding seriously to the Hagerstown Fire Department's need for up-to-date firefighting equipment.
The city has been remiss in replacing equipment about every five years, but will find money to do that, he said.