The ROW used by PATCO on the Philly side ... I know some of it is part of the old Bridge Line ... any history there? Where does the ROW go from 15/16th streets?
There really isn't much beyond 15th/16th Sts. - AFAIK there are some storage tracks but not, for example, an unused tunnel just waiting for rails to provide service to West Philly.
In another thread I noted that in the mid-1970s the DVRPC (Delaware Valley Regional Planning Commission, if you're not familiar with the acronym) laid out a 50-year plan for transit in the s.e. PA - so. Jersey area. Extending PATCO to West Philadelphia was a priority project, with a connection to a similarly-extended P&W along the Cardington Branch as a potential next step.
'fraid it's never gonna happen, at least not in the current economic and political climate.