New York City is full of secret spaces: a hideaway home in a former stable, a Prohibition speakeasy tucked into an outbuilding, a subway tunnel emergency exit concealed behind a townhouse facade. But few such places so capture the imagination as the apartments hidden inside the mansion-like public branch libraries funded more than a century ago by the industrialist Andrew Carnegie. Is there a voracious reader anywhere, after all, who doesn’t relish the idea of living in a library?

In 1901, Carnegie committed $5.2 million (the equivalent of well over $170 million today) for the construction of dozens of neighborhood libraries on land provided by the city. Designed by powerhouse firms like McKim, Mead & White, more than 60 branches were built across the five boroughs, bringing not only books but architectural grandeur to working-class neighborhoods largely deprived of both. Hidden from the public above the elegantly appointed reading rooms, each library typically contained a modest family apartment for a custodian, who performed the punishing work of stoking its coal-fired furnace around the clock.

In the latter half of the century, these custodial apartments were gradually vacated, as the coal furnaces were replaced and the caretakers retired, the last one around 2005. Over the years, many of the units were converted for new library uses, while the remaining dwellings, left to molder for decades, took on a decrepit, ghostly appearance. Today only seven Carnegie apartments survive intact in the New York Public Library system, all uninhabited.

“The first time I saw a Carnegie apartment, I was just blown away,” said Iris Weinshall, chief operating officer of the New York Public Library, which operates 30 Carnegie branches in Manhattan, the Bronx and Staten Island. “Many of them are almost like haunted houses. It’s a pretty eerie feeling.”

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