To bike from Wilmington to Philadelphia?

I would not advise taking Route 13 and Route 291 on a bicycle. Those run through some heavily trafficked industrial areas. If I was to attempt this (and I am BIG chicken - I try to ride only on "bike only" trails, like the Schuykill River Trail), I would come up Route 1. There is still a ton of traffic but at least it is a more rural or suburban area, and there are decently wide shoulders in most places.