Flamboyant oil and gas heir Stanley Marsh 3, who was celebrated for commissioning the famed “Cadillac Ranch” art installation near Amarillo, Tex., but whose life story turned dark when he was charged with sexually molesting teenage boys, died June 17. He was 76.

He had been hospitalized for weeks with “various health issues,” said his longtime attorney, Kelly Utsinger. The lawyer declined to give a cause of death or other details.

Mr. Marsh, who sometimes dressed in colorful outfits, was himself an attraction in the Amarillo area, where he owned several businesses, but he mostly stayed out of the public eye in recent years.

In 2012, after being sued for allegedly having sexual encounters with 10 underage boys, Mr. Marsh was determined by a court to be incapacitated because of a series of strokes and other health problems. The civil suits were eventually settled in a confidential agreement.

Utsinger said that “Cadillac Ranch,” which is one of the best-known public artworks in the country and was immortalized in a Bruce Springsteen song, is on land owned by a trust.

Stanley Marsh 3, left, and photographer Wyatt McSpadden, in 2009 in front of some of the pool balls used as part of an outdoor art project. Mr. Marsh died June 17 at 76. (Betsy Blaney/ASSOCIATED PRESS)

“It will continue; nothing will be done to it at all,” he said.

Mr. Marsh was responsible for several other art projects in the Amarillo area. He installed a 180-foot mock pool table on his ranch, complete with giant billiard balls, and a billboard that simply said, “Actual Size.”

He commissioned “Amarillo Ramp,” an earthwork by renowned artist Robert Smithson. (Smithson was killed in a plane crash in 1973 while surveying the site; the work was finished by his wife, Nancy Holt.)

In the 1990s, Mr. Marsh had numerous diamond-shaped street signs installed across the area that bore sayings such as “Bring Back Public Hanging,” “Road Does Not End” and “Steal This Sign.”

But the project that brought worldwide recognition to Amarillo and Mr. Marsh was the lineup of 10 vintage Cadillacs, each partly buried hood-side down at an angle supposedly the same as an Egyptian pyramid’s.

In 1974, he commissioned an art collective called the Ant Farm to create “Cadillac Ranch.” One of the group’s members, Hudson Marquez, said it was not what the artists had in mind when they first reached out to Mr. Marsh in 1971, seeking funding for a film they wanted to make about a political convention.

“Stanley wrote us back saying, ‘Sounds nice, but I don’t have nothin’ to do with nothin’ that ain’t in Amarillo, Texas,’ ” Marquez said.

They stayed in touch and eventually settled on an installation that would recall a time in post-World War II America when Cadillacs were a symbol of freewheeling possibility. The cars, bought over several weeks from various sources including junkyards, were secured in concrete and formally inaugurated in June 1974. The installation was supposed to be temporary. But word spread, and the artwork that was supposed to be somewhat hidden in a remote area popped up on magazine covers and on TV.

“They are a monument to the American dream,” Mr. Marsh said in a 2004 interview with the Amarillo Globe-News, “when we all thought we could hit the road, get a blonde, break the bank in Las Vegas and be a movie star.”

Springsteen paid tribute in his 1980 song “Cadillac Ranch.”

Stanley Marsh III was born Jan. 31, 1938, in Amarillo and later changed his name to substitute a 3 for the Roman numerals he thought pretentious. His grandfather had struck it rich in the Texas oil boom of the mid-1920s, according to a 2013 profile of the family in the Amarillo Globe-News.

Mr. Marsh graduated from the Wharton School of Business at the University of Pennsylvania with a master’s degree in economic history, then returned to Texas in the late 1960s to oversee the family business. He bought a local TV station that was struggling in the ratings and turned it around, enhancing his wealth.

In the 1970s, his outdoor art and other antics began drawing attention. At the 1975 bribery trial of former Treasury secretary and Texas governor John B. Connally, Mr. Marsh brought a bucket filled with manure to court.

In the realm of art, he had little interest in paintings confined to museums or galleries.

“Art should be two things,” Mr. Marsh said in a 1978 Los Angeles Times interview. “Surprising and hidden from people. Art has to get you out of your mental rut.”

In 2013, Mr. Marsh was indicted by a grand jury on multiple counts of sexual assault and other charges after six teenage boys said they performed sex acts with him in his office. The case had not gone to trial before Mr. Marsh’s death. It was also revealed that Mr. Marsh had reached financial settlements in at least three cases alleging sexual contact with teenage boys dating back to the 1990s.

In light of the revelations, some people in Amarillo called for “Cadillac Ranch” to be bulldozed.

Survivors include Mr. Marsh’s wife of more than 40 years, Gwendolyn O’Brien Marsh, and five adopted children.

— Los Angeles Times