Last month, we discussed the Reading Railroad’s ambitious plans for placing their City Branch below ground level. One part was the construction of a tunnel beneath Pennsylvania Avenue. The tunnel was to be 2888 feet long and of sufficient width to hold four tracks, two for the main line into the city and two for storage.1 At the time, steam power still ruled the rails, so providing suitable ventilation for a tunnel of this length was not a trivial engineering problem. Extensive correspondence over the issue survives in the Reading archives. Ultimately, the problem was solved by placing a series of ventilating grates down the median of Pennsylvania Avenue above, much like Park Avenue in New York City.
A recent featured photograph shows the setting of the keystone at the east portal of the tunnel in 1898 and the completed tunnel in 1900. Construction of the tunnel was not done by boring underground but rather by using the “cut and fill” technique in which the earth is first excavated and retaining walls and roof constructed, after which earth is backfilled on the roof.
Beyond the tunnel, the remainder of the line was an open subway of almost equal length stretching from 20th Street down to 13th Street. At the turn of the century, this was still one of the key manufacturing areas of Philadelphia, and the industries there depended on railroad access. Alongside the tracks that constituted the mainline, the Reading constructed additional sidings and storage yards that served these industries. The unquestionably dominant industry along the City Branch was the Baldwin Locomotive Works, which by 1905 was the largest employer in the region with a workforce of over 15,500 individuals.2
Adjacent to Baldwin Locomotive Works was the plant of William Sellers & Co. at 16th Street. While not as large as Baldwin, the company’s owner designed and successfully campaigned for the use of the first U.S. standard screw thread, which had a major impact on standardization in manufacturing practices.3
The complex trackage in the area allowed Reading switchers to shove freight cars from their subway up an incline to street level and then cross back over the subway tracks on an angled girder bridge into the factory.
Along with the tracks leading into the Baldwin plant between 15th Street and Broad Street, the railroad also built a substantial freight yard on either side of Broad Street. In later years, the air space over these yards would be utilized by constructing buildings over the tracks. The Inquirer Building (actually the Elverson Building, named after the owners) was constructed in 1925 between 15th Street and Broad Street and supplied the Reading Railroad with another customer requiring shipments of newsprint.4
On the east side of Broad Street, the Reading would, in 1930, construct its own multistory warehouse over the tracks, replacing the rather modest one-story freight sheds which had previously occupied the site. The Terminal Commerce Building, as it was called, still stands today and is a beautiful example of Art Deco architecture. While the tracks and many of the industrial buildings are gone today, the pictures remind us of Philadelphia’s rich industrial history that earned it the name of “Workshop of the World”.
 Engineering department notes, Reading Company Collection, Hagley Museum and Library.
 Scranton, P. & Licht, W. Work Sights. Temple University Press, Philadelphia (1986), p. 182.
 #234 The United States Standard Screw Threads (1864) American Society of Mechanical Engineers. Accessed May 25, 2009.
 Workshop of the World. Oliver Evans Press, Philadelphia (1990), pp. 5-43–5-44.