The Flatiron Building in NYC, finished in 1902

Ever since the Flatiron Building was erected at the foot of Madison Square Park in Manhattan in 1902, it has brimmed with tenants, most of which were small businesses.

Songwriters tickled piano keys for sheet-music publishers. Dentists buzzed their drills. At one company, milliners made fezzes for the Masons.

Things began to change after 1959, when St. Martin’s Press moved in and started to expand, snagging offices when other tenants departed. By 2004, its parent company, Macmillan Publishers, had taken over all 21 office floors of the building.

But now, 117 years after the Flatiron opened, those floors are vacant. Lured by cheaper rents downtown and the chance to consolidate staff in a modern workplace, Macmillan moved to renovated floors in the Equitable Building on Lower Broadway earlier this month.

For many in book publishing, the departure marks the end of an era, when authors having meetings at the Flatiron was a rite of passage.

“My publishing life was born and raised in the Flatiron,” said Louise Penny, a best-selling crime writer who even has a Flatiron charm on her keychain. “Behind the breathtaking and famous facade was a rabbit warren, some might say rat’s nest. Books and files were piled everywhere.”

The literary agent Christopher Schelling is equally nostalgic. “Symbolically it means something,” he said of Macmillan’s move, recalling how he often warned his writers that the conference rooms inside the Flatiron were definitely not as stylish as the building’s exterior. But that this was part of the fascination of the place.

“Everyone loves coming to the building,” said Sally Richardson, chairman of St. Martin’s Press, who worked in the Flatiron for five decades. Ms. Richardson helped to organize a goodbye party that drew hundreds of former employees, including some who flew in from other cities.

Although the MAC Cosmetics and Argo Tea stores on the ground level are still bustling, the floors above have been silent since June 14, awaiting crews that will rip out dropped ceilings and sheet rock partitions, among other tasks.

“Right now the building is looking terribly shabby,” said Ms. Richardson, who also spoke of the idiosyncrasies of the heating system — built around cast-iron radiators — that meant she might start her work day wearing a winter jacket and end it in a sleeveless T-shirt. “It’s a quirky place.”