The dispute centers on outsourcing and wages. Also at issue is a union claim that Rotorex laid off 276 workers and hired replacement workers to take their jobs.
The workers were buoyed by the show of support from fellow union members and citizens from nearby Maryland, West Virginia, Pennsylvania and Virginia and as far away as Ohio, Indiana and Illinois.
They held hands and sung the union anthem "Solidarity Forever," at the close of the rally.
The union has sued the company alleging labor board violations, said attorney Stephen Koslow of Washington, D.C., a union lawyer.
"It's our position that the company is acting illegally," he said.
The union went on strike twice, in 1982 and 1985, said Jesse J. Williams, Local 133 president. He vowed to stay off the job until the company recalls all workers back, including the 276 on layoff status.
Production workers earn around $10 an hour base pay although incentives can raise it to $15 an hour.
The union won the right to get unemployment compensation for its members while they remain out of work. IUE President Ed Fire said the union will give $44,000 for the workers in addition to the strike benefits already being provided.
Ron Bowers, a Washington County commissioner and United Auto Workers Union member who spoke at the rally, said even people who don't support unions are against locking out workers who are willing to work.
About half of the Rotorex production workers are women.
Dorothea Dorsey, a single mother of three, worked for the company for 12 years as a general laborer.
"I hope Rotorex comes to its senses, and we can go back to work soon. I have to feed my babies," she said.
Rotorex, a division of the Fedders Corp., makes air conditioning equipment. Company officials could not be reached Saturday.