The Pennsylvania Railroad erected its new main Philadelphia station at 30^th and Market Streets from 1929 to 1933. Designed by the Chicago firm of Graham Anderson Probst & White, 30^th Street Station is a stately combination of Greek and Roman Revival and Art-Deco elements, 637 feet long on the side facing the Schuylkill River and 327 feet wide east to west. The exterior is faced with Alabama limestone. Its main concourse is 290 feet long and 135 feet wide, with a beautiful coffered ceiling rising 95 feet above a Tennessee marble floor. Furthermore, the building incorporated several features that were somewhat novel in station design at the time, such as a chapel, a mortuary, and 3300 square feet of hospital space. An elaborate buzzer/intercom system and a pneumatic tube network were integrated within the complex, providing an efficient internal communication system without compromising the station's monumentality. The reinforced concrete roof of the central concourse was even designed to allow landing space for small aircraft, in anticipation of air service to the facility! Named "Pennsylvania Station" when built, it was the most significant part of the Philadelphia Improvements. And it was one of the last of the old glorious "gateways" to a major American city.

Construction of 30^th Street Station coincided with the onset of the Great Depression, resulting in slower progress than planned. The commuter section of station was the first part to open (on September 28, 1930), before construction started on the main part of the complex. Passengers had to walk through a wooden tunnel past the construction to get to the commuter facilities. On March 12, 1933, through passenger service began, but with only two of the ten main line tracks operational. The station was fully opened on December 15th of that year, but the remaining through-service tracks did not go into service until two decades later.

Unlike Broad Street Station, 30^th Street Station has its passenger through-tracks passing underneath. This arrangement permits the routing of trains traveling north and south without the need to reconfigure the engine and cars. It also keeps local commuter traffic from interfering with this through service, since suburban trains are routed through an attached station above the main terminal, with tracks perpendicular to the main line tracks below. This layout totally separates the two forms of traffic and creates a very efficient traffic flow. (Freight trains bypass the Pennsylvania Station complex entirely by using a very long elevated trestle called the West Philadelphia Elevated Branch—the 1904 "High Line". This is located immediately west of the station.)

There were once plans to integrate the Market Street Elevated-Subway Line with 30^th Street Station. The Market Street Line was an elevated running alongside the terminal in the 1920s, and a new stop at 30^th Street would have been attached to the south side of Pennsylvania Station, similar to the commuter station on the north side. These plans were dropped when the city announced it would extend the Market Street Subway into West Philadelphia and remove the elevated tracks to 44^th Street. (Due to the Depression and World War II, this did not occur until the mid-1950s.) And so today, the Market Street Line's 30^th Street station is not directly connected to 30^th Street Station. An underground passageway linking the two facilities has been closed for years due to security concerns.

30^th Street Station was placed on the National Register of Historic Places on June 7, 1978. The grand passenger station and its trackage have changed little since their construction, although the chapel, mortuary and hospital have long been converted into office space, a conference room, and an infirmary. The internal communication system is no longer used, and neither is the aircraft landing space (if ever). But a food and retail emporium called "The Market at Thirtieth Street Station" opened in the south arcade sometime in the mid-1990s. It was around this period that Amtrak spent over $100 million cleaning, restoring and renovating the structure to its original beauty. Today, Amtrak 30th Street Station is second only to New York City's Pennsylvania Station in national traffic. This makes it the busiest of all inter-city terminals remaining from the years before World War II. The landmark station is mentioned in many novels and is also one of the city's most well-known film locations, with several popular films (Blow Out, Trading Places, Witness) containing scenes shot within. And though the complex is now largely surrounded by the Schuylkill Expressway and other roadways, the absolute scale of the building allows it to retain its architectural integrity and forceful presence.

Suburban rail lines from points north and south come together at 30th Street Station and form a six-track commuter station with three platforms. Proceeding east, the tracks merge from six to four and cross the Schuylkill River on a stately concrete and stone-faced two arch bridge built in 1930. They also cross over CSX's East Side line tracks, which were formerly the B&O Railroad's Philadelphia-Baltimore main line. The tracks then head on a 2.2 percent downgrade over an elevated length of track that replaced the Chinese wall, but is reminiscent of that structure. Twenty-First Street ducks considerably to clear the tracks overhead. At 20th Street, the tracks enter a five-block long subway heading towards Suburban Station, where the four tracks fan into eight. Trains operate very slowly around here due to the maze of curves and turnouts.

The separate subway station (with a closed connection to the commuter rail station) has four tracks, a high island platform  serving the "express tracks" and the Market Frankford subway and two low side platforms serving the subway surface trolley lines.