Welcome back to Period Dramas, a weekly column that alternates between rounding up historic homes on the market and answering questions we’ve always had about older structures.

Grand mansions are emblematic, if not entirely synonymous, with the Gilded Age.

And that’s no coincidence: The Astors, Vanderbilts, Carnegies, and Rockefellers—just to name a few—used their homes, whether in the country or city, to assert their social dominance, establish a legacy, and generate prestige.

Built largely between 1890 and 1915, the houses were often designed by popular architects of the time, most notably McKim, Mead, & White, Richard Morris Hunt, and Horace Trumbauer. As the years marched on, the homes ballooned in size—the Breakers in Newport, Rhode Island, for example, has 70 rooms—setting new standards for opulence by drawing from European palaces to inspire their dazzling interiors.

But the halcyon days of the Gilded Age home didn’t last long. By the 1920s, many of the Fifth Avenue mansions of New York City were being torn down. In the 1940s, it was not uncommon to read about Newport mansions being auctioned off.

Today, the vast majority of Gilded Age mansions aren’t being used as family homes, and very few are still owned by the original family. If they’ve survived the wrecking ball, many have opened as museums. But why? When did they cease to be private residences and start opening to the public?

Between 1910 and 1920, two big taxes were imposed for the first time. In 1913, income tax was introduced, and 1916 brought on the modern estate tax. These new taxes seriously curtailed the previously unlimited funds from which many of the wealthiest families of the Gilded Age were drawing, which suddenly imposed limitations on how they could run their homes.

“These houses were really like hotels,” says Gary Lawrance, architect and founder of the Mansions of the Gilded Age Facebook group and Instagram account. “They had a complete staff doing every little thing that needed to be done. When the money ran out, these places started to fall apart.”

Lifestyles also changed following World War I. “After the ’20s, domestic service started to decline,” says Lawrance. “You could make comparisons with Downton Abbey! WWI changed things greatly—the whole worldview changed.”

And in some places—like New York City—real estate landscapes started to shift. Fifth Avenue, once a residential street known for its impressive array of Gilded Age mansions, was being eyed by real estate developers as it was transitioning into a commercial thoroughfare.

A New York Times article from 1928 features an interview with the developer Benjamin Winter, and explains his multi-million-dollar deals with the Vanderbilts and Astors like this:

“A home now worth $4,000,000 at its present land value is obviously costing $240,000 a year if capitalized at 6 percent,” Winter explains. “Add to this taxes, servants, and other items and the annual upkeep reaches $400,000, which explains why the wealthiest families are content to sell their mansions.”

For the record: $400,000 in 1928 money would be over $5.5 million when adjusted for inflation.

Alice Vanderbilt sold 1 West 57th street—the grand mansion lauded as the largest house in Manhattan—for $6.1M (about $83.2M in today’s dollars) in 1925, citing how expensive the taxes were on the property. The mansion was demolished to eventually make way for the luxury department store Bergdorf Goodman.

Before the Vanderbilt mansion was demolished, the house was opened to the public. People could purchase a ticket—proceeds went to charity—and tour the principal rooms.

This was not an isolated event: In 1927, the home of mining tycoon and politician William A. Clark allowed the public to tour its 147 rooms before the house was demolished to make way for Rosario Candela’s 960 Fifth Avenue. Admission cost 50 cents and was donated to charity.

The New York Times reported that Charlie Chaplin was among those touring the rooms, which included a banquet hall lined in paneling from Sherwood Forest of Robin Hood fame. While the house would be demolished, some rooms were saved and moved to the Corcoran Gallery of Art in Washington, D.C., where they can still be viewed today.

By the end of the 1920s, very few of the Fifth Avenue mansions remained. “Last Summer the Astor mansion at Sixty-fifth Street was removed,” says an article in the Times that announced the sale of the Clark mansion. “The Phipps house is to go soon, and Judge Elbert H. Gary, who settled at Sixty-seventh Street twenty years ago, certain that he never would be disturbed, has turned his property over for an apartment improvement.”

The article, which reads like an obituary for Gilded Age mansions, suggests that the few remaining houses will soon fall to the hands of developers. That suggestion proved to be true.

Outside of New York, the Biltmore Estate in Asheville, North Carolina, was opened in 1930 as a way to revitalize the local economy following the Great Depression. Cornelia Cecil, who inherited the 250-room house from Cornelia’s father, George Washington Vanderbilt II, commented: “We feel in doing this, it is a fitting memorial to my father. After all, it was his life’s work and creation.”

Over the next few decades, other grand houses followed suit, slowly transitioning away from family homes to residential museums. In 1948, The Breakers in Newport, Rhode Island, opened to the public, when the owner Countess Szapary leased it for $1 per year to The Preservation Society of Newport County. In 1949, the New York Times reported on the decline of Newport society—even when the houses were for sale, it was difficult to find anybody to buy them.

Marble House—another Vanderbilt mansion in Newport—started to open sporadically in the 1950s after sitting vacant for a number of years. It officially became a museum in 1963, also at the hand of The Preservation Society of Newport County.

It was not uncommon to see these mansions—and all of their contents—be sold at auction. “At The Elms in Newport,” Lawrance says. “When the owner, Mrs. Berwind, died, she willed it to a distant nephew who wanted nothing to do with the mansion. He decided to sell it to developers. Then the Preservation Society stepped in and bought it back at the very last minute to save it from being torn down. By that time, all the original contents, which had been intact since 1901, had been dispersed.”

Thankfully, many of the pieces have been returned to The Elms, which opened in 1962 to the public, although some of what you’ll find in the house is furniture in the style of what was originally there.

Not every mansion landed on the auction block. When the Phipps mansion in Old Westbury Gardens, New York, was opened to the public in 1959, nearly all of the its interiors were intact. “About 85 percent of the furnishings stayed here in Westbury house,” says director of preservation Lorraine Gilligan. “The taste of the Phipps family is reflected in every room.”

Gilligan said that when Peggy Phipps Bergner inherited the house from her parents, she quickly realized that she was unable to maintain the house. She then decided to move into a smaller house next door, and open the house and its impressive gardens to the public with a little help from her friends and relatives. They did everything from help empty out drawers filled with clothing to bringing over new bedspreads to spruce the place up.

But while these houses may have ceased to be residences for the families who once called them home, they are now open for all to see—an being looked after by organizations dedicated to their preservation.

If you look closely, in some cases, they get a little use by their original owner: Descendants of Countess Zsapary (of the Breakers) can still use the third floor of the mansion as their own residence.

And Gilligan says that Peggy Phipps Bergner would sometimes come over to borrow a vase for a dinner party—that is, when she wasn’t driving around the grounds of Old Westbury Gardens: “When she was in her 90s, she had a caretaker who would bring her around the gardens on a golf cart with her Yorkie. She liked greeting children and talking to people. It was like her yard, after all!”