It put the “Upper” into the East Side. It prevented Fifth Avenue from becoming Wall Street. It made “penthouse” the most important word in real estate.

The elevator did more than make New York the city of skyscrapers, it changed the way we live, as German newspaper editor Andreas Bernard explains in “Lifted.”

“The elevator played a role in the profound reorganization of the building,” he writes. That means a shift from single-family houses and businesses to apartments and office buildings. “Suddenly . . . it was possible to encounter strangers almost anywhere.”

The elevator, in other words, made us more social — even if that social interaction often involved muttered small talk and staring at doors. It also reinforced a social hierarchy; for while we rode the same elevators, those who rode higher lived above the fray. Elisha Graves Otis, who perfected the elevator in Yonkers, helped usher in terraces and corner offices, high-rise apartments and rooftop clubs.

So, what would New York be like without elevators? Besides a lot thinner, Bernard offers three things that changed thanks to Otis’ innovation.

They invented the high life

Before the elevator, buildings in New York basically were limited to six stories because people wouldn’t walk any higher. Even when the elevator raised the roof to 12 stories, developers faced a threat greater than technology — snobbery.

Upper floors were seen as servants’ quarters or the attic apartments of the poor. Bernard quotes from Joseph Roth’s “Hotel Savoy,” whose main character stays in the unwanted upper floors. “Those who lived on high were in the depths, buried in airy graves, and the graves were in layers above the comfortable rooms of the well nourished guests sitting down below, untroubled by the flimsy coffins overhead.”

Even after elevator buildings began appearing in New York, it took years to convince tenants to live in the upper reaches. In the first commercial building with an elevator, the Equitable Life headquarters, the insurance company took the lower offices, while the eighth floor held the custodian’s apartment.

Even in 1884, when the Dakota opened on the Upper West Side (the first apartment building geared to the rich), it was assumed the wealthy would rather live closer to the ground.

Bernard quotes historian Elizabeth Hawes, who says in the original plans for the Dakota, “the largest apartments [were] in the lower two floors . . . because elevators were still something of a novelty and not entirely trusted. . . . [The architect also] reasoned that lower-floor living would seem more familiar to New Yorkers who were accustomed to living in town houses. The eighth and ninth floors were to be used exclusively as laundry rooms, service and storage rooms, and servants’ rooms.”

It wasn’t until the 1920s that sky-high living really caught on. Developer Emery Roth planned top-floor apartments with terraces; Roth’s biographer, Bernard says, is the person who introduced the word “penthouse.”

Roth’s Ritz Tower, as 465 Park Ave., is the building that Hawes credits with New York’s love affair with altitude. Built in 1925, “it effected a new attitude toward an aerial city and an aerial home.

“Penthouse and terrace apartments because fashionable and proliferated,” she writes. “Style-conscious tenants staged parties on terraces and planted gardens in the air.”

They made mansions extinct

As New York moved away from individual houses to shared apartment buildings, there was angst among the wealthy. How could they be expected to interact with the rabble?

When the first apartment house was built in 1869, Bernard notes, it was already equipped with a rear service stairway to keep the plebeians away.

It wasn’t only the rich who were worried, however. Bernard highlights a 1907 article, “The Radical Evil of Life in Apartment-Houses” from American Architect and Building News. By mixing classes, the magazine warned, the less wealthy will try too hard to keep up with the Joneses. “Disliking to be outshone, [they] will also try to make a splurge and will sacrifice its children’s rights to a ‘plush rocker,’ a piano, or a too expensive dress.”

The end result? “That means debt, sooner or later, and debt too often means drink.”

To prevent this calamity, luxury apartments segregated using elevators. The Dakota was the first to have service elevators for deliveries — while many of the passenger elevators led to the entrances of only one or two apartments, preventing needless interaction.

One of New York’s grandest neighborhood transformations hinged on this quest for privacy.

The Upper East Side was once dominated by individual mansions. But around 1920, developers coveted that land for apartments.

“The divorced wives of great industrialists like William K. Vanderbilt II or Edward Hutton agreed to the demolition of their mansions only on condition that it would not affect the exclusivity of access to their new upper-story apartments,” Bernard writes.

He quotes a newspaper article from 1926 that says one house, on the corner of Fifth Avenue and 92nd Street, was torn down and then rebuilt — on the 12th floor of an apartment building that replaced it.

Barbara Woolworth Hutton had a 54-room mansion that she gave up for a massive apartment. But only after, Hawes writes, “they cut a private porte cochere into the side of the building, which gave entrance to a private elevator that ascended directly to a three-story suite that filled [the building’s] crown.”

While a few mansions remain in Manhattan, the elevator — and in particular the private elevator — made castles in the sky the new status symbol.

They kept the financial district ‘lower’

By the 1860s, Bernard writes, New York’s financial district was so crowded that city planners briefly considered moving it uptown. When companies became successful, they expanded sideways, not up.

That changed in 1870, when the Equitable Life Assurance Society, the largest insurance company in America, constructed its headquarters at 120 Broadway.

Equitable’s CEO, Henry B. Hyde, decided on an eight-story building with two elevators, at the cost of $30,000, Bernard writes, “perhaps on the basis of his early friendship with Elisha Otis.”

Hyde himself oversaw the renting of the upper floors. It was a tough sell, but that eventually changed. In 1897, the rent for ground-floor space was $8 per square foot, and $3 for the top floor, Bernard says. Within a decade, those numbers were reversed.

Architect George B. Post, who was a technical adviser on the Equitable Building, rented offices on the top floor himself and soon was able to sublet for a higher rent than he originally paid.

It was lawyers, Bernard says, who first appreciated the upper levels, which, he quotes from Equitable’s history, “were full of light and free of dust and far above the noise of the street.”

Soon, the top-floor corner office became the CEO status symbol, and the financial district began building up — solving Wall Street’s space problem and creating a new race to be the top dog.

History of the elevator in NYC

1854 — Elisha Graves Otis, who founded the E.G. Otis Elevator Company in Yonkers, demonstrated his invention at the Crystal Palace on 42nd Street. Otis didn’t really invent the elevator; he invented a safety mechanism that stopped it from crashing to the ground. Despite the popular myth, Otis’ demonstration hardly was remarked upon in the press at the time, Bernard says.

1857 — Eder V. Haughwout’s fashion emporium installs the first passenger elevator in the city. The building (which still stands today at 488-492 Broadway) was only five stories and didn’t need one, but Haughwout thought the novelty would attract more customers. He was wrong. Three years later, it was removed because the public refused to accept it.

1870 — The eight-story Equitable Life Assurance Building at 120 Broadway is the first office building to install passenger elevators. In the next two decades, having an office on an upper floor (particularly a corner office) becomes a sign of status.

1875 — The elevator makes it feasible to build to about 11 stories, Bernard writes, and a number of “elevator buildings” are constructed to this height. It’s not until the 1880s, with the introduction of steel-framed construction, that buildings go higher.

1884 — The Dakota, at 72nd and Central Park West, is the first building to have service elevators to keep the riffraff away from the wealthy residents. Developers tried to convince the rich to move away from private mansions in favor of mansions in the sky with the promise of private elevators.

1913 — Improvements in steel-frame construction and elevator speed and safety leads to the construction of the 55-story Woolworth Building at 233 Broadway, considered the world’s first skyscraper.

1922-23 — Developer Emery Roth constructs twin 15-story buildings, Myron Arms and Jerome Palace, at Broadway and 82nd. He designed top-floor apartments with terraces on all sides, thus introducing the word “penthouse” to the real-estate lexicon. Mansions on the Upper East Side are increasingly torn down in favor of luxury high-rises.