Teamsters spokeswoman Barb Maynard said the drivers have been victims of "persistent wage theft" from employers because they are treated as independent contractors instead of employees.
Most of the drivers are independent contractors for trucking companies. The truckers had said they face shrinking wages and becoming actual full-time employees of the companies would mean better wages and workplace protections.
The trucking companies said the unhappy truckers were a vocal minority and a labor stoppage would have been disastrous while the industry still recovers from a recent dockworkers strike.
Earlier this year, tough contract negotiations with dockworkers nearly closed 29 seaports from San Diego to Seattle. The port complex in Los Angeles and Long Beach is the primary West Coast gateway for hundreds of billions of dollars of annual trade with Asia.