When it was originally opened in 1953, the terminal consisted of the main block (now Terminal B/C) and two concourses, which are today's Concourses B and C. Around 1960, Concourse D was added to the eastern side of the building. For most of the "regulated" jet era, Concourse B was used by American, Allegheny, National and Delta. Concourse C was home to Eastern, TWA and Northeast. Concourse D was used by United, Northwest Orient and Mohawk.
Like PHLBOS said, there was a small pier extending from the west side of this terminal. It was called Concourse A and was used for international flights by BOAC, Air France, Lufthansa, Pan Am and TWA. Customs and immigration were located in the southwest corner of the 1953 terminal building. These facilities were closed in 1972 when international flights moved to the blue overseas "barn" on the east side of the airport.
As the PHL
website says, the big rebuild for the terminal came in 1977, when the single terminal (now US Airways' Terminal B/C) was replaced by four unit terminals, each with their own ticketing and baggage claim. Originally there were supposed to be five, but construction on Terminal A was stopped. The building remained a concrete shell for about fifteen years until it was finished out and opened as the international concourse (now A-East) in 1991. Unit Terminals B and C were "re-consolidated" back into a single facility for US Airways in the late 1990s.
When originally opened, Concourses B, C and D were all two stories, although there were no jetways. Passengers walked along a second-level concourse to their designated gate, then took a stairway down to apron level and boarded their gate. Jetways were added to most of the PHL
gates starting in the late 1960s and continuing through the 1970s. When Terminal E was built as part of the 1977 reconstruction, all of its gates had jetbridges.