NEW YORK • Sam Shepard, a reluctant movie star and one of the most significant American playwrights of the 20th century, died last Thursday at his home in Kentucky. He was 73.

A spokesman for his family announced the death on Monday, saying the cause was complications of amyotrophic lateral sclerosis or Lou Gehrig's disease.

Possessed of a stoically handsome face and a rangy frame, Shepard became a familiar presence as an actor in films that included Days Of Heaven (1978), The Right Stuff (1983) and Baby Boom (1987). He bore a passing resemblance to that laconic idol of Hollywood's golden era, Gary Cooper, and in an earlier age, Shepard could have made a career as a leading man of westerns.

Instead, he was more at home as one of the theatre's most original and prolific portraitists of what was once the American frontier. In plays such as True West (1980), Fool For Love (1983) and the Pulitzer Prize-winning Buried Child (1978), he dismantled the classic iconography of cowboys and homesteaders, of American dreams and white picket fences, and reworked the landscape of deserts and farmlands into his own shimmering expanse of surreal estate.

In his plays, the only undeniable truth is that of the mirage. From early pieces such as Chicago (1965), written when Shepard was in his early 20s and staged in the margins of off-off-Broadway, to late works such as Heartless (2012), he presented a world in which nothing is fixed.

That includes any comforting notions of family, home, material success and even individual identity. "To me, a strong sense of self isn't believing in a lot," Shepard said in a 1994 interview with The New York Times. "Some people might define it that way, saying, 'He has a very strong sense of himself.' But it's a complete lie."

That feeling of uncertainty was translated into dialogue of an uncommon lyricism and some of the strangest, strongest images in American theatre. A young man in Buried Child, a bruising tale of a Midwestern homecoming, describes looking into the rearview mirror as he is driving and seeing his face morph successively into those of his ancestors.

Shepard wrote more than 55 plays, acted in more than 50 films and had more than a dozen roles on television. He was also the author of several prose works, including Cruising Paradise (1996) and the memoir Motel Chronicles (1982).

Though he received critical acclaim almost from the beginning of his career and his work has been staged throughout the world, he was never a mainstream commercial playwright.

In the relatively naturalistic True West, two brothers of opposite temperaments find themselves assuming the personality of the other. Actors John Malkovich and Gary Sinise made their names in the Steppenwolf Theater Company production while Philip Seymour Hoffman and John C. Reilly memorably traded off the parts in the 2000 Broadway revival.

Roles within families depicted onstage continually shift and dissolve, as in Shepard's great A Lie Of The Mind (1985), the title of which might serve for every play he wrote.

As for love between a man and a woman, Shepard, whose long relationship with actress Jessica Lange cast an unwanted spotlight on his private life, described that as "terrible and impossible".

They became a couple after appearing together in Lange's star vehicle Frances in 1982. Previously, Shepard had been married to actress O-Lan Jones. In 1984, the year he and Jones divorced, Shepard starred with Lange as a struggling farming couple in the film Country, cementing an image of the two of them as noble outsider celebrities. Famously, they lived out of the show business orbit in Virginia farm country near Charlottesville, Virginia. They never married and split characteristically under the radar almost a decade ago.

Shepard always regarded Hollywood stardom warily, but he became a major crossover celebrity, showing up on lists of America's Sexiest Men.

"Sam was so hot in Resurrection," his then wife Jones later said of his 1980 film with Ellen Burstyn, "that I wrote him a filthy fan letter."

Daniel Aukin, who directed Fool For Love on Broadway two years ago, said Shepard told him of his illness before they began working on the production. But the playwright largely kept his battle private.

He is survived by his children - Jesse, Hannah and Walker Shepard - and his sisters, Sandy and Roxanne Rogers.

Born Samuel Shepard Rogers III on Nov 5, 1943, he came naturally by his Strindbergian view of love, marriage and family. The father for whom he was named was an alcoholic, nomadic man, and he haunts Shepard's work, in the ghostly form of the cynical, romantic narrator of Fool For Love and the title character of The Late Henry Moss (2005).

Known as Steve Rogers through his childhood and adolescence, the younger Shepard grew up on his family's avocado farm in Duarte, California. He briefly attended Mount San Antonio College as an agriculture student, but dropped out to move to New York in 1962, having discovered jazz and the plays of Samuel Beckett.

The actor was soon writing plays in which characters and images melded into one another, suggesting a poetically cadenced LSD trip. He wrote songs with John Cale and Bob Dylan, notably Brownsville Girl, from Dylan's 1986 album Knocked Out Loaded, and he played drums for a time in a group called the Holy Modal Rounders, who once opened for progressive rock group Pink Floyd. He also had a well-publicised relationship with singer-songwriter Patti Smith.

Besides acting in films, he directed a few, including Far North (1988), which he wrote and which starred Lange. He wrote or collaborated on screenplays for, among others, directors Michelangelo Antonioni (Zabriskie Point, 1970), Robert Frank (Me And My Brother, 1969) and Wim Wenders (Paris, Texas, 1984).

Speaking of how he creates his characters, Shepard once perfectly summed up the artful ambiguity that pervades his work: "There are these territories inside all of us, like a child or a father or the whole man... and that's what interests me more than anything: where those territories lie.

"I mean, you have these assumptions about somebody and all of a sudden this other thing appears. Where is that coming from?

"That's the mystery. That's what's so fascinating."

NYTIMES, WASHINGTON POST