The urban idea of stacking people's homes one on top of the other is very old: The Romans thought of it; so did the Egyptians. In European cities and in New York, by the early 1800s, the constraints of space meant squishing rooms for the lower classes into tenement buildings a few stories tall.

Apartments, though, were different. They were something in between—not the stand-alone homes and townhouses that were, in the 19th century, becoming the province of the urban rich and at the same time not a couple of rooms for large families, with a shared bathroom in the hallways. Apartments were for the middle class, the creative class. They were kind of cool.

If any city pioneered apartments on a large scale, it was Paris. Sharon Marcus, a professor of comparative literature, writes in Apartment Stories:

Throughout the nineteenth century, the apartment house dominated the Parisian urban landscape, inspired and worried domestic ideologues and urban planners, and provided fiction writers with settings… Their popularity owed much to two factors: They provided spatially compact housing in a city with a rapidly increasing population and offered an expanding middle class opportunities for investing in relatively inexpensive and profitable properties.

More than London, Marcus writes, Paris in the early 1800s embraced the apartment. And when wealthy Americans came to Paris for their cultural education, their interest was caught by these "Parisian flats." In New York, nothing like that existed—a large, well-appointed space in a building that happened to be shared with other families. Tenements didn't have parlors.

Two New York architects in particular—Calvert Vaux, who helped design Central Park, and Richard Morris Hunt—liked what they saw, and in the late 1860s, Hunt convinced Rutherford Stuyvesant, one of New York's wealthiest men, to build the city's first middle-class apartment building, at 142 E. 18th St., just a couple blocks from Union Square.

The Stuyvesant Apartments needed the right tenants to succeed, though. They needed to show middle-class New Yorkers that sharing life in a building could be a respectable way to live. And its designers succeeded in attracting a very fashionable–if eccentric—group: The widow of George Custer, who lived on the first floor; George Palmer Putnam, who published Washington Irving and Edgar Allan Poe; the founder of the National Rifle Association; Elizabeth Jordan, one of the first editors of Harper's Bazaar; and Calvert Vaux, eventually, lived here, too. Rent was anywhere from $1,000 to $1,800 per year, which today would be at somewhere between $25,000 to $46,000. (This is a rough estimate, as the Bureau of Labor Statistics only calculates inflation going back to 1913.)