The crash happened around 12:00 p.m. at Delaware Avenue.
The driver, Michael W. Heffner, 50, Downingtown, PA, was transported to Christiana Hospita for a hip injury.
Police say, for an unknown reason, Heffner's vehicle drifted off the west edge of the roadway causing the trailer to strike the guardrail.
Heffner attempted to get the trailer back into the right hand lane of southbound I-95, however the trailer overturned, dumping a load of rocks in the roadway.
Traffic was being diverted onto I-495 in Claymont while the crash was cleaned up.
The highway reopened about 3:10 p.m.
