I recently came across a neat new book called "Forgotten Philadelphia" which has photos and brief essays about various structures that have been demolished over the years.
http://www.amazon.com/Forgotten-Phil.../dp/1592135064

Anyway, the author devotes a chapter to various plans that didn't come to fruition. One thing I hadn't heard of was the proposal to connect the Main Line to Chestnut Hill via a parkway. It would have started at Lancaster Ave in Ardmore, followed Mill Creek road, over the Schuykill, then Cathedral road, over the Wissahickon, then connected to the Lincoln drive extention near Pastorius Park in CH.

I've always wondered why Cathedral Road is so wide, with a median strip, behind the Andorra shopping center. It's especially odd the way it continues around past the horse stables and then abruptly ends. Perhaps it was built that way with the parkway in mind.

According to the book, the project dates back to the 1880's, was close to implementation in the 1920's, but was scrapped for good in the 1950's.