My mother, a lifelong New Yorker, often guided me on what I thought of as ghost walks of New York. Not, however, to search for haunted houses or to attempt communion with the dead, but simply as a remembrance of what had gone before. What was once the Schwab mansion on Riverside Drive, encircled by a glorious and extensive private garden, was demolished in 1948 to make room for Schwab Houses, an apartment complex occupying an entire block. And, as a novelist, she recalled time spent at the splendid old Random House offices on Madison Avenue and 50th Street, themselves created from the impossibly gilded Villard Houses. Now, the only original parts of the building that remain are the entrance to the Helmsley Palace Hotel along with several enticing public rooms. There were homelier ghosts too, like the little Hungarian bakery near her apartment, its fragrant spaces razed 20 years ago to allow a high-rise to loom featurelessly into the sky. And there is the odd memory of what my family continued to call the “Nazi movie theater” on East 86th Street, once the heart of a German neighborhood. Long after it had become a perfectly respectable member of a cinema chain, my parents remembered certain movies that were shown there in the 1930s.

Several years ago, American Heritage temporarily moved our offices about 10 blocks north to 23rd Street, to what at first seemed something of a wasteland; nothing dramatic, just a little drab except for the Flatiron Building, which gives the district its name. Before long, change was in the air, and now I have my own ghost memories of 23rd Street. The parking lot at the corner of Sixth Avenue became a pretty-good-looking not-too-high-rise co-op building; Home Depot, of all things, chose to open its first Manhattan outlet next door to us, in the same Beaux-Arts building the long-gone department store Stern Brothers inhabited in 1878. Across 23rd, a small brick building set back from the street that I’d scarcely noticed burned fiercely one afternoon. One person was hurt, the structure still stands, and a remarkable history flared to life. This unprepossessing place had been the home in 1901 of Evelyn Nesbit, Stanford White’s 16-year-old-mistress, and her notorious red velvet swing.

Another surprising survivor made itself known to me during daily walks in Madison Square Park, these days beautifully re-landscaped and emerging from its fairly recent scary reputation into an urban jewel. One day, I noticed a marker in front of a tree that, tall and leafy as it was, looked like every other tree in the park. I stopped to see what made it special and learned that this 60-or-so-foot pin oak had come to the park in 1936 as a seedling from the Montpelier, Virginia, estate of President James Madison, presented to the city by the Fifth Avenue Association to mark the centennial of the 1836 opening of Madison Avenue.

I suppose a lunchtime circumnavigation of the park isn’t travel in the strictest