How New York City invented the penthouse

1930s
"Penthouse: the word conjures up luxury and exclusivity. Thing is, it’s a clever 1920s rebranding of the top of a building, where no one with any choice used to want to live. For most of the city’s history, the single-structure mansion was the preferred domicile for the rich. At the turn of the 20th century, monied New Yorkers were increasingly occupying 'French Flat' cooperative apartments. But even then, the undesirable rooftop apartment was given over to servants. Until the city and its tastes changed in the Jazz Age. ..."
Ephemeral New York