Police have cleared the scene of the accident on the Schuylkill Expressway. It happened in the eastbound lanes in West Conshohocken, just east of the Blue Route interchange.
Two cars and two trucks all collided around 7 a.m. Both of the cars were wedged into the rear end of one of the trucks.
Police were able to get one lane open to traffic fairly quickly, but the jam still backed up for miles.
Two people were hurt.
The wreckage was moved off of the highway just before 9 a.m., but the backup continued from the accident scene at the I-476 interchange all the way back to the Pennsylvania Turnpike.