Before the old station was torn down, a steel structure was built over the existing train tracks and platforms. On top of it rose a new Madison Square Garden — the fourth arena bearing that name. (The original opened on Madison Square in 1879.) So although the glories above are long gone, when you get on or off a train at Penn Station now, the platforms resemble the original ones from 1910.

Compared with later campaigns to defend important structures, the effort to stop Penn Station’s destruction was pathetic. Modernist architects, including Philip Johnson and Robert Venturi, signed petitions denouncing the “vandalism” planned for the station, citing its status as a Beaux-Arts landmark, but an on-site protest march on Aug. 2, 1962, attracted no more than 200 people.

Flinching at the prospect of a surging cash hemorrhage, the Port of New York Authority, as it was then called, showed no desire to adopt the old structure.

The design for a new Madison Square Garden was rendered in banal mid-1960s corporate vernacular by the architect (and former president of Pepsodent and Lever Brothers) Charles Luckman, who — referring to McKim’s Pennsylvania Station — admonished a reporter not to regard buildings as monuments “to the architect or to the owner.” The Pennsylvania Railroad’s president, Allen J. Greenough, observed that the structure was built “not primarily as a monument at all but as a railroad station.”

In 1968, the railroad merged with the New York Central to become Penn Central, which went bankrupt within two years.

Happily, the loss of Penn Station stimulated public institutions devoted to historic preservation, along with stricter rules and more intense citizen activism in New York and elsewhere. This made it easier to save Grand Central Terminal when it was endangered in the mid-1970s.

In the early 1990s, Daniel Patrick Moynihan, then a Democratic senator from New York, began an effort to transform at least part of the James A. Farley Post Office (opened in 1914 and also designed by McKim’s firm) across Eighth Avenue from Penn Station into a worthy successor to McKim’s old neoclassical palace. Plans include moving Amtrak service to the new terminal (to be named after Moynihan), reducing some congestion at the badly overcrowded Penn Station, with its maze of rail, commuter rail and subway traffic. Progress on Moynihan Station is moving ahead slowly, with an estimated price tag of as much as $1 billion a major sticking point.