Comissioned by Cornelius Vanderbilt's son, William H. Vanderbilt, the Vanderbilt Twins were born when William bought an entire block of Fifth Avenue and built two mansions: one for him and his wife, and the other for his two daughters.

The William K. Vanderbilt Mansion, built under the direction of his wife Alva, was a departure from what had been a tradition of the city's rich living in unassuming homes. The "Petite Chateau" marked a new age of sumptuous building.

While the original Vanderbilt mansion on this spot was a much more restrained townhouse, Cornelius Vanderbilt II took his cues from his brother and other society families. He bought the five neighboring townhouses and replaced the original home with a mansion based on the Chateau de Blois.

Built for prominent lawyer and philanthropist Eldridge T. Gerry by famed architect Richard Morris Hunt. Gerry, and his family lived in this mansion until his death in 1927. It was then sold and torn down to make way for the famous Pierre Hotel.

Though now replaced by the blue-blooded Knickerbocker Club, this spot was once home to the Josephine Schmidt Mansion. Josephine's husband had been a successful brewer, and she built this limestone chateau in 1899 following his death. However, it was not to last long. In 1909 she married the son of an Italian prince and moved to Europe. The Knickerbocker Club purchased the mansion in 1914 and tore it (and its neighbor) down to build their clubhouse.

Though it is named for its builder, the wealthy J.J. Astor, the true master of this beautiful French Renaissance twin mansion was his mother Caroline Astor. J.J. took the southern half, while Caroline, the arbiter of the New York's social scene and presider over the "400" took the north. It was here that New York's two most awaited balls would occur. First, Caroline Astor would hold hers and then exactly week later J. J. Astor would throw his own.

H.O. Havemeyer, the scion of a family that dominated the sugar business, had architect Charles C. Haight build this mansion. While its turreted exterior is simple, the house was famed for its lavish interiors designed by Louis Comfort Tiffany and Samuel Coleman.

George Gould, heir to railroad magnate Jay Gould, built not one, but two mansions on this site! Initially, he built a neo-Gothic structure, but the style quickly went out of vogue. Not a man to be outdone, Gould razed his old home and erected a new Italianate mansion here.

Though W.C. Whitney was, in fact, the third owner of this Renaissance style mansion built by Robert L. Stuart, he invested enough to make it his own. Whitney spent over a million dollars in an interior renovation project that Stanford White oversaw.

Not all mansions had to take over vast swaths of real estate. Stockbroker Josiah Fiske and his neighbor John Sloane both had more modest (though still quite lavish) homes fronting Fifth Avenue.

The Frick Mansion was built by one of the Gilded Age's most ruthless robber barons: Henry Clay Frick. Partner of Andrew Carnegie, Frick amassed an enormous fortune in the steel industry and used some of it to build this beautiful mansion. Now home to the Frick Collection, Frick always intended his house to become a museum, creating it to highlight his collection and stipulating in his will that it should be open to the city.

Built by William A. Clark, the mansion was dubbed "Clark's Folly" due to its extravagance. Costing more than five million dollars, the home was most likely the most expensive American home ever built up until that time.

The site of both railroad titan Henry Cook's mansion and tobacco magnate James Duke's home, 1 East 78th Street certainly lives up to Henry Cook's conception of the area. Cook bought up not only this lot but the lots surrounding it, selling them slowly to ensure only the "right people" moved in.

Designed by Stanford White and completed after his death, the Payne Whitney house was rendered in a high Renaissance style. It, in fact, was so in keeping with that theme that a statue White bought in Italy for the house's rotunda was unknowingly sculpted by Michelangelo.

Built for banker Isaac Fletcher, this French Gothic mansion was donated to the Met (along with all of Fletcher's artwork) upon his death. The Met promptly sold the home (to endow Fletcher's collection) to Harry Sinclair, an oil magnate who would end up in jail due to the Tea Pot Dome scandal. It is now the Ukrainian Institute of America.

Modeled on the 16th century Chateau Chenonceaux in France’s Loire Valley, Issac Vail Brokaw built his mansion to include everything from mosaics to murals, even a moat! Sold after his death to the Campagna corporation (which built many of the co-ops on Fifth Avenue), its demolition was a wake up call to preservation activists.

Carrère & Hastings built the William Starr Miller straight off their success with the main branch of the New York Public Library. A 64-room Louis XIII mansion, it survives to this day as the Neue Galerie, a space that celebrates 20th century German and Austrian art.

Built by James Speyer, the Louis XVI mansion served as a constant to home to Mrs. Speyer's charitable endeavors. The home's eventual demise was the consequence of one: it was donated to the Museum of the City of New York, whereupon it was quickly sold and demolished.

Just like his business partners Frick and Carnegie, Henry Phipps built his own mansion on Fifth Avenue. Trowbridge & Livingston designed this Italianate Renaissance mansion, set back from 87th Street to allow for a semi-circular driveway. However, it was not to be occupied for long. Henry Phipps, desiring something more modest 😲, moved out after a few years. Phipp's descendants would eventually move to their own apartment building at 1 Sutton Place South (see our Candela Tour) and the mansion was sold to Daniel Guggenhiem ten years after it was built.

Andrew Carnegie purposefully built his mansion farther uptown than his contemporaries, causing the surrounding areas (remote at that time) to be named Carnegie Hill. Modeled after an English Georgian manor, many were disappointed by its intended modest design (relative to contemporary mansions, of course.) It was the first private home to have an steel frame and the first in the city to have a residential Otis elevator. The Mansion now serves the Cooper Hewitt Museum.

One of the largest private homes ever built in Manhattan, the Otto H. Kahn house's exterior is remarkably restrained, making it possible to pass it without recognizing it for what it is. Following Kahn's death in 1934, the home was occupied by the Convent of the Sacred Heart, New York's oldest girls' school, which remains here to this day.

When examining the plans for this mansion, Jacob Schiff warned its builder ( banker Felix Warburg) that it might exacerbate the anti-Semitism of the New York social scene. Luckily, Warburg ignored his father-in-law's misgivings and built the beautiful mansion that now houses the Jewish Museum.

Designed by Delano and Aldrich, the Willard D. Straight House was built for the diplomat Willard Straight and his wife Dorothy Payne Whitney in an unassuming Federal style. Serving as the home for the International Center for Photography for a period, it is now a private residence again.