What Happened to the Gilded Age Mansions of New York City?

Why? Because the palatial Gilded Age mansions of New York City have almost completely vanished. Starting around 1880, New Yorkers built some of the largest and most elaborate houses the country had ever seen. On Fifth Avenue, Riverside Drive and elsewhere in the city stood free-standing homes modeled after European palaces, some with more than 100 rooms and spanning entire city blocks. Yet within a few decades, virtually all of these massive houses had been demolished. “These amazing mansions that were built along Fifth Avenue—many of them have been destroyed,” said Helen Zoe Veit, an associate history professor at Michigan State who is a historical consultant for the HBO show.

In the 1880s and ‘90s, the city’s most desirable residential neighborhood was Vanderbilt Row, a stretch of mansions on Fifth Avenue between 50th Street and the southeast corner of Central Park. Today the area is a frenzied commercial district of office buildings and retail stores, with virtually no trace of the posh single-family homes that once stood there.

For example, William K. Vanderbilt and his social-climbing wife, Alva Vanderbilt—the inspiration for Bertha Russell on “The Gilded Age”—lived in a white limestone château occupying nearly a full block at Fifth Avenue and 52nd Street. “If you see pictures of it, it just blows your mind that this was on Fifth Avenue, and that anybody would build a house in such an ostentatious château style,” said Esther Crain, author of “The Gilded Age in New York, 1870-1910.”

Indeed, elite architecture in the Gilded Age was all about one-upmanship, she said. With great fortunes being made along with the country’s industrialization, newly wealthy families vied to show off their riches by spending millions—tens or sometimes hundreds of millions in today’s dollars—constructing massive houses. “It was all about the show—I’m wealthier than you,” said historian Tom Miller, author of “Seeking New York: The Stories Behind the Historic Architecture of Manhattan—One Building at a Time.”

Things had changed dramatically by the 1920s, however. Federal income taxes had made huge mansions financially unsustainable, plus it became harder to find the armies of servants required to maintain them. During the building boom of the ‘20s, many were razed to make way for commercial use or multistory apartment houses, which were billed as modern and convenient.

In the Gilded Age, “if you had any kind of standing in the city and wealth, you wanted your own single-family home,” said Ms. Crain. By the 1920s, however, “if you had a lot of money, you probably would prefer to live in an apartment building because the building took care of everything for you.”

A few Gilded Age-era mansions—such as the Frick Collection and the Cooper Hewitt design museum—remain intact on the Upper East Side. Midtown, however, saw scores of grand homes destroyed, Mr. Miller said. “The houses south of 59th Street just got wiped out because of the commercial district,” he said. And farther west, nearly all of the 30 or 40 large mansions that once lined Riverside Drive have also been replaced with apartment buildings, Ms. Crain said. Mansions in Brooklyn’s fashionable St. Marks District in Crown Heights met a similar fate.

“These were very special buildings that should have been preserved,” said Mr. Miller.

Read on for a closer look at the vanished mansions of Gilded Age New York, and some of the rare structures that remain.

Morton F. Plant House, 649 Fifth Ave.

Completed: Circa 1905

Rooms: Roughly 50

Cost of land and construction: $750,000, about $24.1 million today

Today, office workers and tourists passing the Cartier flagship store on the traffic-clogged corner of Fifth Avenue and 52nd Street in Midtown would never suspect that the six-story, Renaissance-style building was originally a private home. The house was built for Morton F. Plant, son of the railroad and shipping tycoon Henry Plant, according to the city’s Landmarks Preservation Commission.

Mr. Plant bought the land for about $350,000 in 1902, according to the book “Great Houses of New York, 1880-1930” by Michael C. Kathrens, and spent about $400,000 building the house. It had roughly 50 rooms, including a music room, a men’s smoking room and 12 staff rooms.

Cartier purchased the house in 1917—around the time wealthy families were abandoning the neighborhood in the face of encroaching commercial development—and converted it into a jewelry store, preserving much of the building’s original appearance: a pediment on the 52nd Street facade has two carved cornucopia.

The story goes that the Plants traded the house to Cartier in exchange for a $100 and a $1 million string of pearls that Mrs. Plant admired. Inside, the space retains its massively high ceilings.

As the only Midtown mansion to remain intact, Mr. Miller said, “the Plant mansion gives us an idea of what Fifth Avenue looked like.”

Petit Château, the William K. Vanderbilt and Alva Vanderbilt mansion, 660 Fifth Ave.

Completed: Circa 1882.

Number of rooms: Roughly 40

Cost to build: $3 million, about $83.5 million today

Sold for: Roughly $3.75 million in the 1920s

Demolished: 1926

Today, 660 Fifth Avenue is a 39-story office building with Zara, Uniqlo and Hollister stores at its base and hoodie-clad mannequins in its shop windows. But on this site once stood a massive home, designed by Richard Morris Hunt and modeled after a 16th-century French castle. Nicknamed Petit Château, the house had a slender 3-story turret carved with fleur de lis at the entrance. A two-story, stone banquet hall was 50 feet long. The home cost $3 million, about $83.5 million today, according to “Fortune’s Children: The Fall of the House of Vanderbilt.”

With its pale Indiana limestone exterior, the house was far different from the brownstones that New York’s elite had favored up until that point, according to the architect and historian Gary Lawrance, who estimated that the house had 40 rooms. “You take a neighborhood of brownstones and stick a dazzling white limestone house in the middle of it—that really broke the mold of what had been there prior,” he said. Petit Château is perhaps best known as the setting for a grand costume ball Alva Vanderbilt threw for about 1,200 guests in 1883.

It was sold for $3.75 million in the 1920s and razed in 1926.

The Cornelius Vanderbilt ll mansion, 1 West 57th Street

Completed: Circa 1883

Number of rooms: about 91

Cost of land and construction: $3.375 million, about $94.8 million today.

Sold for: Roughly $7.1 million

Demolished: 1927

…