Mrs. Whitney stands with jockey Fernando Jara in Saratoga Springs in 2006. (Jim McKnight/AP)

Marylou Whitney, an aspiring actress who married into one of America’s wealthiest families and became a sought-after hostess and noted philanthropist supporting hospitals, sporting organizations and the arts, died July 19 at her estate in Saratoga Springs, N.Y. She was 93.

Her death was announced by the New York Racing Association, which did not cite a cause.

The daughter of a Missouri accountant, Mrs. Whitney settled in Saratoga Springs in 1958 after marrying Cornelius Vanderbilt “Sonny” Whitney, an heir to oil and rail fortunes who co-founded Pan American Airways, raised champion thoroughbreds and also had business ventures in mining, banking, agriculture, lumber and movie production.

A high-profile socialite who counted President Gerald R. Ford, former British prime minister Winston Churchill and Princess Margaret of England among her acquaintances, Mrs. Whitney was known for planning dramatic entrances at opulent affairs. She arrived at soirees at times in a hot-air balloon, a pumpkin-shaped carriage or astride a horse dressed as a unicorn.

Her own bashes were all-in affairs; she convened one fete with an invitation featuring an image of herself in an upward-blowing white dress, standing over a subway grate a la Marilyn Monroe in the 1955 movie “The Seven Year Itch.” At her Palm Beach, Fla., estate, she once proposed a party featuring live elephants, but neighbors raised persuasive objections.

Marylou and Sonny Whitney owned properties as far-flung as a horse farm in Lexington, Ky., and a villa on the Spanish Mediterranean island of Mallorca, but Mrs. Whitney’s main residence was an old country manor sitting on 135 acres in Saratoga Springs called Cady Hill House.

In a life spent dripping in jewels and swirling on dance floors to the music of big-band society orchestras, she also used her social standing to bring attention and money to her favored causes, including equine hospitals and research. She was known as “the Savior of Saratoga” for the largesse she lavished on the once-depressed horse-racing mecca north of Albany. Her deeds were chronicled in publications as diverse as the Daily Racing Form and Vanity Fair.

In Saratoga Springs, she was a founder of the performing arts center and helped establish the National Museum of Dance and Hall of Fame. She also worked to restore the National Museum of Racing, only a few blocks from the historic racetrack.

She funded the Saratoga Backstretch Appreciation program that hosted family activities and cookouts for track employees and supported a Saratoga-based equine welfare organization, the town’s YMCA, several local parks and the hospital.

Marie Louise Schroeder was born in Kansas City, Mo., on Dec. 24, 1925. She briefly studied drama at the University of Iowa but dropped out after her father died when she was 19.

She returned to Kansas City and became a radio personality. In 1948 she married Frank Hosford, a member of the John Deere farm machinery family, and was separated from him when she met Sonny Whitney, 26 years her senior and thrice divorced, at a nightclub in Phoenix. He helped produce the only film in which she (billed as Mary Hosford) had a role, “The Missouri Traveler” (1958), which starred Lee Marvin and Brandon De Wilde.

She and her husband were major patrons of Manhattan’s Whitney Museum of American Art — started by Sonny Whitney’s mother, Gertrude — and the 1980 Winter Olympics in Lake Placid, N.Y.

Sonny Whitney sold many of his racehorses beginning in 1984, saying at the time that he did not want to burden his wife with the responsibility for them after his death. The classic Eton blue and brown racing colors of the C.V. Whitney Racing Stable were retired and later given to a nephew.

Sonny Whitney died in 1992 at 93, and Mrs. Whitney reportedly inherited $100 million. As a widow, she formed Marylou Whitney Stables and repurchased many of the horses her husband had sold a decade earlier. Her stable produced many champions, including Birdstone, the 2004 Belmont and Travers Stakes winner.

In 1997, Mrs. Whitney married John Hendrickson, an aide to Alaska Gov. Walter J. Hickel who was almost four decades her junior. (Mrs. Whitney had ties to the state, including sponsorship of a team of sled dogs for the 938-mile Anchorage-to-Nome Iditarod race.)

Soon after their marriage, Mrs. Whitney appointed Hendrickson president of Whitney Industries, the family’s lumber and gravel business. He is now president of the National Museum of Racing.

Besides her husband, survivors include five children.

“The security of being rich is pleasant,” Mrs. Whitney once told Palm Beach Life magazine. “But there is a responsibility — setting examples, charity. I think I could be just as happy being poor. I’ve been both.”