I posted this in P8 and will place it here for folks who haven't seen it there.
Three maps showing originally envisioned versions of the Philadelphia subway system.
This map depicts the originally proposed 1912 system. You can see certain ideas that were altered or never came to fruition including the full route of the South Broad Street subway to League Island (Navy Yard), an elevated route along Woodland Avenue as well as subway/elevated lines to Germantown & Chelten Avenue and the first phase of the Roosevelt Blvd. subway. Also shown are the routes for the Parkway/29th Street line (the Walnut Lane Bridge was built with provisions for the never built subway) and the originally envisioned route for the Frankford El to a terminal at Rhawn Street. You'll also note the Center City delivery loop and a Chestnut Street subway.
This map depicts the 1923 finalized system - after completion of the Market Street subway and Frankford El. The Broad Street subway was under construction at the time. You'll note the Walnut Street subway that would have fed into the Woodland Avenue El as well as the Eighth St/Ridge Avenue subway. Also, the Chestnut Street trolley subway is depicted along with the Parkway line feeding directly into the Broad Street Subway at City Hall as was originally intended (hence the odd turn the line makes north of City Hall - it was not to avoid the building foundations - it was to allow for an easier connection to the Parkway line.) The Chestnut Street line would have began at Franklin Square.
This is a more detailed look at one version of the Center City loop with a track map. This version was new to me when I saw it. Instead of the Parkway line feeding into the Broad Street Subway this version has it feeding into the delivery loop via 16th, Walnut and 8th Streets before taking Ridge Avenue to meet with the North Broad Street trunk.
