Sadly, it took a five-alarm fire and the needless deaths of two firefighters for most Philadelphians to learn about the old Buck Hosiery factory. As the flames died down, we also learned about an unresponsive, ineffective city bureaucracy that failed to seal the building, and about the tax-dodging, Brooklyn-based property parasites who treated the building and the neighborhood around it with contempt.

Many Philadelphians, I suspect, never actually saw the building or the Kensington neighborhood where it presided for more than a century. It was in one of those "deindustrialized" parts of the city that has been neglected for a long time; it wasn't on the tourist itinerary.

Over the past two decades, I have visited the Thomas W. Buck Hosiery building once or twice a year, first as a graduate student learning about urban history and later as a professor. In a city filled with architectural treasures, it was one of my favorites. I admired its redbrick simplicity and the unadorned, unpretentious regularity of its windows and pilasters, which made a purely utilitarian building from the late 19th century seem like a piece of early modernism. I loved the pride with which it announced its name in big block letters: Buck Hosiery. It even dated itself right below the name, which was very helpful to historians like me.

I felt as if I were visiting an elderly, ailing friend. Each time I got off the El, I hoped the building had gotten the care it deserved. But it never really did, despite a few hopeful false starts. And now, of course, it never will.

It joins a long, sad, and growing list of industrial architecture erased from Philadelphia's landscape. It includes the enormous Stetson Hat plant that burned to the ground in 1980, the carpet factory that burned near Third and Cecil B. Moore in the 1990s, and several of Buck's own neighbors. The buildings that made Philadelphia the "workshop of the world" are fast disappearing.

But this is not merely one historian's lament for the relics of a bygone era. Buck Hosiery was certainly part of Philadelphia's industrial past, but as many in its neighborhood recognized, it could have been part of the city's future, too. Several Philadelphia neighborhoods have been revitalized with the help of their historic resources.

The first such success was Society Hill, where neglected pieces of the city's 18th-century heritage were combined with modern development to create one of the most attractive urban areas in the country. And if Society Hill demonstrated what could be done with 18th-century rowhouses, Manayunk showed the potential of old mill buildings. More recently, Old City, Queen Village, and Northern Liberties have been reinvented through the recycling and repurposing of old buildings.

Historic buildings are often architecturally unusual or unique, offering something different from the same old, prefabricated same old. More than that, they connect our present with our past. And that is what gives neighborhoods their character, and gives us a sense of civic identity.

When the evidence of our past disappears, we lose more than buildings; we lose part of our collective sense of place. Unassuming though it was, there was not a building exactly like the Buck Hosiery building anywhere. When it went up in flames, we lost some of our future as well as some of our past.

Steven Conn is the author of "Metropolitan Philadelphia: Living with the Presence of the Past" and the director of public history at Ohio State University. He can be reached at conn.23@osu.edu.