The U.S. Border Patrol intercepted the vehicle late last week at a checkpoint along Interstate 5 between San Diego and Orange County.
The driver, a U.S. citizen whose name was not released, was turned over to the Drug Enforcement Administration this weekend, a Border Patrol spokesman told the Los Angeles Times.
The 53-foot trailer was checked by a sniffer dog at the San Clemente checkpoint's secondary inspection and found to be carrying 218 boxes packed with pot. The cargo weighed in a 18,458 pounds and was valued at nearly $15 million.
"This seizure by our agents helps weaken the transnational criminal organizations who attempt to use our roadways to conduct their illegal activities," San Diego Sector Chief Patrol Agent Paul Beeson said in a written statement.