Amazon workers at four California facilities joined their striking colleagues on the picket line Thursday morning after reaching a stalemate during labor negotiations.

The union is calling the action the largest strike against Amazon in American history. “The corporate elitists who run Amazon are leaving workers with no choice,” the International Brotherhood of Teamsters’ General President Sean M.

Employees at facilities in City of Industry, Palmdale, Victorville and San Bernardino are trying to unionize under the Teamsters.