There comes a point in the life of our workhorse industrial buildings when we stop seeing them for the marvels they perform, and soon after that, we stop seeing them altogether. In Philadelphia, which abounds with the unused relics of a mighty industrial past, it's all too easy to forget that these are the structures that made the city modern.

Such has been the sad fate of the art deco steam plant behind 30th Street Station, built in 1929 by the architects of the rail terminal, with the same progressive ideas and design skill. Although the plant's octagonal smokestack soars 323 feet off a six-story base, making it one of West Philadelphia's tallest structures, one wonders how many of the thousands of passing commuters ever consciously note its presence. In two weeks, it could be gone, unceremoniously deleted from the skyline by Amtrak.

A building that churned out steam and electricity may not sound like a big deal. But the plant enabled the Pennsylvania Railroad - one of Amtrak's ancestors - to shift its main depot from Broad Street in the heart of Center City, to downtown's perimeter on 30th Street.

That allowed the railroad to electrify its train fleet and tear down the loathsome Chinese Wall tracks, paving the way for Market Street to become Philadelphia's premier high-rise office corridor - a modern business center. Those accomplishments are one reason the steam plant was listed on the National Register of Historic Places.

As a result of the planned implosion, which could take place as early as Nov. 15, Philadelphia will lose not only a landmark - living evidence of its railroading heritage - but also a structure that might have provided an incubator for a new, more up-to-date, industry.

Yet Amtrak can't even provide a straight answer about why the steam plant - along with a dormitory built for Pullman porters and a small outbuilding - must be demolished right now, nearly half a century after they were mothballed. The steam plant, of course, is contaminated with asbestos and PCBs, like all generating stations. It's not in the best condition either, which isn't surprising for a building that has been shuttered since 1964.

You could say similar things about other temples of industry around the city, including a couple of magnificent power stations on the Delaware waterfront, dozens of North Philadelphia factories, and the Reading Viaduct. We're only just starting to appreciate those hard-working structures and recognize that they're as worthy of preservation as monuments and grand houses. The hope is that if you let industrial buildings be, someone will come along with a new use.

Actually, just a few years ago, Amtrak's real estate department thought it had one for its steam plant. After clinching a deal for the Cira tower in 2002, both the plant and Pullman dormitory were proposed as anchors for an expanded office park on the station's west side, nestled in a crook of land below Drexel University's campus.

Consultants were hired and preliminary drawings were made. At the time, an Amtrak official led me on a tour of the area so I might understand the potential.

The real estate bust obviously put a damper on Amtrak's planning, but that doesn't mean the exercise wasn't worthwhile. For decades, Philadelphia has cherished the dream of developing the underused real estate around the train station and filling in the lifeless chasm that keeps downtown and the universities from becoming a unified whole. Some day, that dream and the real estate market will be aligned.

Train stations such as 30th Street are perfectly poised to attract knowledge industries eager to be close to transit, communication lines, and universities. One hurdle to development is the location of Amtrak's electrified rail lines along the Schuylkill. They require construction of a hugely expensive building platform. In contrast, the flat land to the west, where the steam plant stands for now, is practically ready for construction.

At the time the development plans were being considered, it seemed the steam plant's survival was guaranteed by its architectural pedigree. Because the plant was erected in preparation for the grand new rail terminal, the Pennsylvania Railroad assigned the design to the same architect: Graham, Anderson, Probst & White, the firm that took over from the famous Chicago architect and planner Daniel Burnham.

The steam plant didn't get the full limestone treatment, but the result still has the noble stature of a bank or library. The art deco trimmings must have made the workers who tended its turbines feel they were part of a great, city-building enterprise. An unusual, eight-sided stack, 21 feet in diameter, towered over the station. Its dramatic outline still holds its own on the west bank skyline, though now it's wedged between Cira and Drexel's new Millennium Hall tower.

The design for the Pullman dormitory, by the same architects, was modest, but its history is also intriguing. The building housed sleeping quarters for the mostly African American Pullman porters, the corps of uniformed railroad attendants who are credited by historians with laying the groundwork for the civil-rights movement. Those black porters were restricted to the basement, while other workers enjoyed better rooms on the upper floors. It's possible the first stirrings of protest began with conversations in that dank basement.

It's no wonder that, when Amtrak broached plans to demolish the structures, both the city and state historical commissions protested. City records show that the Historical Commission asked Amtrak to analyze the costs of retrofitting the buildings to lease to outside tenants.

Amtrak's response was that post-9/11 security concerns made it impossible to bring in outside tenants. The two commissions eventually acquiesced to Amtrak's plans. Yet, Amtrak's security concerns would imply that the railroad's land holdings could never be developed - a serious blow to Philadelphia. Somehow, those issues aren't stopping New York and Chicago from building in their rail yards.

Retrofitting industrial buildings like the steam plant requires greater creativity and perseverance than other projects, though not always more money. Preserving the industrial past is one way cities can remember their roots. The steam plant helped Philadelphia become a modern manufacturing metropolis. If Amtrak understood the potential of its rail yards, it could return the favor a second time.

Contact architecture critic Inga Saffron at 215-854-2213 or isaffron@phillynews.com.