Hugh O'Brian, who shot to fame as Sheriff Wyatt Earp in what was hailed as television's first adult Western, has died. He was 91.

A representative from HOBY, a philanthropic organization O'Brian founded, says he died at home Monday morning in Beverly Hills.

Until "The Life and Legend of Wyatt Earp" debuted in September 1955, most TV Westerns — "The Lone Ranger," ''Hopalong Cassidy," the singing cowboys' series — were aimed at adolescent boys.

"Wyatt Earp," on the other hand, was based on a real-life Western hero, and some of its stories were authentic. (The real Earp, who lived from 1848 to 1929, is most famous for his participation in the 1881 "Shootout at the O.K. Corral" in Tombstone, Arizona.)

Critics quickly praised it, and it made O'Brian a star.

"If we were doing Westerns with the chase and the fights that last endlessly, and the sheriff's daughter in sunbonnet and calico and the Wanted posters ... we wouldn't reach the audience we reach each week," O'Brian once said.

"Gunsmoke," which debuted just a few days after "Wyatt Earp," became an even bigger hit, and by 1956-57, both were in the top 20 shows. In the 1958-59 season, Westerns accounted for an incredible seven out of the top 10 U.S. television series, including No. 1 "Gunsmoke" and No. 2 "Wagon Train," with "Wyatt Earp" at No. 10.

"Wyatt Earp" remained a Top 20 hit until 1960, but it was canceled the following year after being supplanted by the avalanche of other adult Westerns.

O'Brian, meanwhile, continued to work frequently in movies, television and theater through the 1990s, although he never again achieved the prominence he enjoyed as Wyatt Earp.

He starred in the 1970s detective series "Search" and appeared in such films as "In Harm's Way" and "Ten Little Indians," and reprised his role as Earp in 1994's "Wyatt Earp: Return to Tombstone," a film that combined new footage with colorized scenes from the original black-and-white TV show.

He also had a small but memorable role as the faro dealer in John Wayne's last film, "The Shootist," and later noted with pride that it gave him the distinction of being the last bad guy killed by Wayne. (Wayne himself is reputed to have met the real Wyatt Earp as a young man in Hollywood in the 1920s.)

Late in his career, O'Brian made frequent guest appearances in television series and variety shows and toured in the national companies of "Cactus Flower," ''1776" and "Guys and Dolls."

O'Brian had originally planned to study law at Yale University. But after actress Ida Lupino saw him in a play at a small Los Angeles theater she cast him in "Never Fear," a 1949 film she was directing, and his acting career was launched. He went on to appear in small parts in such films as "The Return of Jesse James," ''Red Ball Express," ''Broken Lance" and "There's No Business Like Show Business."

O'Brian was inducted into the Hall of Great Western Performers of the National Cowboy and Western Heritage Museum in 1992.

He also made his mark in philanthropy as founder of the Hugh O'Brian Youth Leadership organization.

In 1959, impressed by the work of Albert Schweitzer, O'Brian made a pilgrimage to the 83-year-old savant's settlement and hospital in central Africa. Although his journey was derided by some critics as a publicity stunt, the actor dismissed the remarks, telling reporters how his life had been changed by the Nobel Peace Prize winner.

Shortly after returning home, he founded the youth group. Each year, it brought together promising high school sophomores at sites around the country for leadership seminars. In 1999 O'Brian estimated that HOBY had more than 200,000 graduates from ages 16 to 59. He received numerous awards for his achievement.

Born Hugh Krampe in Rochester, New York., O'Brian was educated in Winnetka, Illinois, leaving school at 17 to join the Marines. He went on to become one of the corps' youngest drill sergeants.

In June 2006, at age 81, O'Brian wed 54-year-old Virginia Barber at the Forest Lawn Memorial Park cemetery in what they quipped was a "wedding to die for."

"I said goodbye, early this morning, to my favorite cowboy. My 28 years with Hugh have been an amazing, beautiful adventure. I will miss my special man who told me every day that I was beautiful and that he loved me," his wife wrote Monday. "I was one lucky cowgirl."

The couple, who had dated for years, honeymooned in England, studying philosophy at Oxford University.

"I think, quite frankly, an active mind is as important as an active body," O'Brian told The Associated Press at the time. "Fortunately, my lady's a teacher and she puts up with me."

It was his first marriage, but his romances were many and well publicized, especially his fling with Princess Soraya, the ex-wife of the shah of Iran. In 1969 he faced a paternity suit in which he was judged to be the father of the 16-year-old son of a Los Angeles photographer. He was ordered to pay $250 monthly support for the boy, whose name was Hugh Krampe Jr.

"I sure had my share of fun and an awful lot of ladies," he recalled in that 2006 interview.