One of the more puzzling things about the Market Frankford Line is the lack of a station between 15th and 30th Street stations. Especially when you consider that today, all of the city’s tallest office buildings are clustered between 17th and 20th Streets, along Market. After all there are 5 stops east of 15th along Market. Then none west of 15th until the the subway crosses under the Schuylkill River to 30th Street.
To understand how this happened, you have to understand the topography of Philadelphia when the El was constructed. The might Pennsylvania Railroad’s Broad Street Station brought passengers from across the region to Philadelphia via a viaduct that ran adjacent to Market Street. The two-story tall viaduct was known as the “Chinese Wall” to locals and with its noisy, smoking trains and dark underpasses, left the area west of Broad as an undesirable address.