Macmillan completed the move of its trade group June 19 from the celebrated Flatiron Building to new offices in Lower Manhattan. We asked CEO John Sargent to share what it was like to work at the Flatiron, and his feeling about leaving one of New York’s most famous buildings.

One day in the spring of 1996, I picked up the ringing phone on my desk at DK. It was Tom McCormack, the iconoclastic CEO of St. Martin’s Press. He invited me to his office for lunch. I remember thinking, “Now I can get inside the Flatiron Building.” And also, “Would Tom stick to his widely rumored routine and have half a tuna fish sandwich and a glass of milk?”—he did.

I recall my awe while walking into the building for the first time, and my shock when it took five minutes to get to the 18th floor. I would later learn that these were the last water-powered hydraulic elevators in New York City.

Twenty-one years later, a group of us met, in the same chairs and at the same table where Tom and I had eaten lunch, to decide if we had to leave the Flatiron. When word got out that our decision was imminent, two small posters started to appear randomly throughout the building. First there was Remain, with the R superimposed on the Flatiron Building. Then there was Flexit.

When you come in through the west-side entrance of the Flatiron, there is a plaque on the outside, erected in 1989 by the National Park Service, that designates the Flatiron as a National Historic Landmark, and states that the building “possesses national significance in commemorating the history of the United States of America.” Another plaque below that one, placed there in 1958 by the New York Community Trust, proclaims that “it was one of the early buildings to employ a steel frame,” a precursor to the skyscrapers to come. Some claim that the Flatiron was the tallest building in New York when it was built in 1902. The Flatiron Building is famously graceful on the outside but—though it’s rarely disclosed—disheveled on the inside.

St. Martin’s Press moved into that less-than-ideal interior 60 years ago with a lease for one-half of the 18th floor, 4,000 square feet, which housed the trade and college divisions. We added more space every few years, until 15 years ago, when we took over the entire building. In the early years, we were tied closely to Macmillan in London. Harold Macmillan, who had returned from a stint as prime minister of the U.K. to once again head his family business, occasionally came to visit his American outpost. Employees at SMP (two have been here for more than 50 years) recall forming a line from the elevator so that he could shake hands with the entire staff on his way in. There is history here.

The building gives up that history slowly; you learn her secrets over the years. I recall standing at the window in my office a year or two after I had started. I was pondering something, and, glancing down, I saw the curved wooden base of the window frame. Wait. How does a curved wooden window frame last for almost a hundred years? I took out my pocketknife and began scraping. I felt metal under the many layers of paint. Another scratch or two and I discovered copper. I kept going and found that all the windows in my office were copper, as were most in the building. There are stairs hidden behind walls and under sidewalks from when there was a speakeasy downstairs. We discovered, about a decade ago, that the outside wall of the basement was fake—for reasons unknown.

But with the ever-growing list of charms and wonders came an ever-growing list of horrors. The view from the top roof is amazing! But this isn’t a desk, this is a card table in what used to be a closet. They have put in new handmade balustrades! But the radiators are clanging so loudly I can’t think. The Empire State Building lights up as the sunset dims, but the new toilet stalls on the eighth floor are so small that I can’t actually sit down.

Starting all those years ago, the people of SMP, then Tor, and later many of the rest of Macmillan’s publishers and support staff have endured physical discomfort. They have worked in small warrens, too cold in the winter (bring your down parka to work), too hot in the summer, and with little hot water. But they have also worked in what many claim is the most photographed building in the world.

If you walk downtown toward the intersection of 23rd Street, Broadway, and Fifth Avenue, the first view of the Flatiron is arresting, with that remarkably thin, decorated prow splitting Fifth Avenue and Broadway. Thrilling architecture for all to see, but I always think of the people. There up top, behind the fluted columns, Sally Richardson. Below her Tom Dunne. And below him, on 16, Jen Enderlin. She sits in her great friend Matthew Shear’s old office, he of the kind eyes, booming laugh, and gap-toothed grin. He would have been happy to see her there. Two floors down is Tom Doherty, legendary founder of Tor, his office awash in awards and the mass market paperbacks that started it all. They were all here before I came, most of them for decades.

Flexit was in full swing for more than a month, and the Flatiron now stands empty. We say goodbye to Jeff and the other owners, to Sunny Atis and the rest of the building staff. They have been a part of us for many years.

There have been a lot of tears in the building in recent weeks, but also some singing, wall painting, and hallway drinking games. The reports from the early waves who have moved downtown to the Equitable Building at 120 Broadway are hugely positive. The new space is spectacular, and it has amenities never dreamed of by the denizens of the Flatiron. We are happy to start anew in another historic building.

The last words about our time at the Flatiron go to David Rotstein of SMP. He says it better than I can, and I suspect that he had a hand in designing those Remain posters. “The place we called home was the most beautiful and famous building within the greatest and most famous city in the whole world. It was the place where we lived our lives, the place where we grew up—as a company, and as individuals. And this most special of homes was ours and no one else’s. Family members only. And so, walking over the threshold for one final time is a difficult moment for sure.”