On a frigid January evening in 2016, just two weeks into Mayor Kenney's tenure, a historic, 19th-century apartment house off Rittenhouse Square erupted in a gusher of flames and smoke. Because the fire had been incubating in an air shaft before anyone noticed, it was unusually hot and spread quickly. By the time firefighters contained the blaze, the roof had collapsed, the grand oak staircase was reduced to kindling, and fat icicles hung like stalactites from the windows. An engineering report prepared for the owner concluded that the brick building was a total loss.

Such declarations have typically been treated in Philadelphia as the final word on the matter, the equivalent of an architectural death sentence. But in this case, the Department of Licenses and Inspections pushed back. Commissioner David Perri personally requested a second opinion, one that focused on what it would take to renovate the historic structure, rather than on how badly it had been compromised, according to a statement from his office.

By reframing the problem, the report helped convince Marc Ginsburg, who owns William Penn Realty, that reconstruction was feasible. It took his company more than a year of painstaking work, but today you would never know that the Georgian Revival apartment house at 2122 Locust was once a smoldering ruin. A new fourth floor has been stitched onto the building, using a red-and-black brick pattern that perfectly matches the original. The elaborate notched cornice, which was left a tangle of twisted tin after the fire, is back where it belongs. Power-washed and freshly pointed, the whole place gleams.

As you might guess by now, this is one of those man-bites-dog stories. Historic structures are being demolished almost daily across Philadelphia, and their remains carted off to the garbage heap without so much as a "nice to know you" from city officials.

Mayor Kenney, who once promised to give the city's preservation laws real teeth, rarely mentions the issue any more. The task force he formed 16 months ago to look for solutions to the preservation crisis has yet to produce any recommendations. The bulldozers keep coming.

So why did 2122 Locust have a happy ending, and how can the results be replicated elsewhere?

For starters, the restoration is a testament to what the city can achieve when top officials decide to make preservation a priority. Perri played a crucial role here, just as he did in February, when he ordered the owner of a Civil War-era apartment house on Second Street in Old City to preserve its cast-iron facade after a similarly devastating fire. Those pieces are being stored off-site until reconstruction can begin.

The other big reason for the survival of these two apartment houses is that they had the good fortune to be in a city-managed historic district. That meant that they immediately came under the jurisdiction of the Historical Commission, as well as L&I, after the fires. The Locust Street building is also listed individually on the city's Historic Register.

Yet, as we know, plenty of worthy older buildings don't get the same love from the city. Those two success stories stand in sharp contrast to a recent case involving the Frankford Chocolate & Candy building, one of the last intact Civil War-era factories on Washington Avenue in South Philadelphia. The massive compound was already listed on the National Register and had just been nominated for the city's Historic Register, when developer Ori Feibush bought the property for $15.5 million. Even though the chocolate factory had a strong chance of being designated a landmark by the city, Feibush made no secret of his intention to replace it with a mix of apartments and million-dollar townhouses.

To do that, he needed a crisis. While the factory had never suffered a major fire, it had been neglected by its previous owners. After bricks started popping off the facade, Feibush brought in engineers, who concluded the building was in danger of collapse. L&I subsequently issued a code violation deeming the factory "imminently dangerous."

That happens to be the same designation that 2122 Locust received after the fire. According to a building professional who toured both buildings, the chocolate factory was in much better condition than 2122 Locust and could have been easily stabilized. Instead, Feibush applied for a demolition permit.

In this case, L&I did not push back. In an interview this spring, Perri told me that he personally believed it was possible to save the chocolate factory, but he had no independent evidence to challenge Feibush's engineering reports. For some reason, neither Perri nor the Historical Commission sought an independent assessment, despite the urging of the Preservation Alliance. "We had to go with" the recommendations of Feibush's engineers, Perri insisted.

Why the different treatment for the chocolate factory? One explanation may be that the chocolate factory didn't look like a typical historic building. Even though it dates from the late 19th century, just like the buildings on Second and Locust Streets, it wasn't built as a home for a wealthy family or designed by a famous architect. As an industrial relic, located well outside the city's original core, it isn't valued in the same way.

It also seems likely that the two apartment houses got extra attention because both are part of handsome architectural ensembles that define their neighborhoods and provide vivid, physical evidence of the city's development.

Built in 1899 as a single-family house for Charles T. Cresswell, a prominent lawyer, 2122 Locust marks the spot where Rittenhouse Square's fashionable set switched from the exuberant Victorian style to a more conservative, neocolonial look. Every house to the west of Cresswell's, between Van Pelt and 22nd Street, adopted the same restrained Georgian Revival demeanor. You can literally see that arc of history by walking down the block. Perri wisely understood that losing one piece would unravel the whole group.

Still, 2122 Locust might not have been brought back to its original splendor if Ginsburg had contested the findings of the second engineering report. Ginsburg also hired a preservation consultant, Powers & Co., to help him apply for federal tax credits, which will significantly offset the $2.5 million reconstruction.

Although Ginsburg complains that the Historical Commission "put us through the wringer," he is pleased with the result: 16 brand-new, one-bedroom apartments that are now being rented for around $1,800 a month. One bonus from the renovation is that he uncovered a trove of interior details — from stained glass to mosaic floors — that had been obscured by past renovations.

All that would have been lost if Ginsburg had treated the "imminently dangerous" designation in the same way that Feibush did. L&I is right to be vigilant about protecting public safety, but as the experience at 2122 Locust shows, it can be the most powerful advocate for preservation the city has.