In "Blackthorn," Sam Shepard, as an aging Butch Cassidy, rides in with all the grizzled wisdom and well-worn danger of the true American West.

Director Mateo Gil's drama, now in theaters, imagines the bandit as a refugee from his own myth, living in Bolivia in the 1920s under the name James Blackthorn while facing down an old foe (Stephen Rea) and a new outlaw protégé (Eduardo Noriega).

It's a lion-in-winter turn, and though the straight-shooting 67-year-old playwright and actor researched Cassidy heavily, he says he approached the role feeling no extra burden.

"I can't say I thought about Butch in terms of mythology," says Shepard, relaxing in a booth at the Mercer Hotel.

"The thing about going that route is, it takes on a conceptual way of thinking, and takes you away from the character.

"After all, mythological figures don't walk around knowing they're mythological.

The myth grows out of [their] sweat."

And what about feeling like he was treading on sacred ground, given the Paul Newman/Robert Redford classic "Butch Cassidy and the Sundance Kid"?

"Nope. I know what sacred ground is, and that aint't it!"

Shepard himself has built his share of mythology and walked plenty of sacred ground. The son of an Army officer who grew up mostly in California, Shepard worked on ranches and played music before coming to New York in the '60s and waitering at the Village Gate.

He wrote his first plays while living on Avenue C.

"I arrived here almost at the very moment that Off- Off-Broadway started," says Shepard. "La Mama, Theatre Genesis, Judson Poets, the scene at St. Marks Church — all of them exploded like mushrooms.

"As a writer, the great thing was I could literally write something in a week, see it go into production the next week, and the third week there was an audience!"

His "La Turista" at the Theater at St. Clement's Church took a 1967 Obie for Distinguished Play. Later, as Shepard played music with former girlfriend Patti Smith and toured with Bob Dylan's Rolling Thunder Revue, plays like "The Tooth of Crime" and "Curse of the Starving Class" made his name.

He won a Pulitzer in 1979 for "Buried Child," a year after he made his first major film, "Days of Heaven." That led to "Frances" (where he met his future love, actress Jessica Lange) and "The Right Stuff," which earned him a 1983 Oscar nomination for portraying test pilot Chuck Yeager.

"When I started acting, I had a tremendous fear of the camera, so I'd try to hide from it, which is impossible," he says.

"But the more I did it, I got away from that. Now, in acting, I'm available to a lot of things that I wasn't."

Though Shepard only regrets turning down one project — the seminal miniseries "Lonesome Dove" — he says in the '80s, as he did more movies ("Country," "Baby Boom") while writing his best-known plays ("True West," "Fool for Love," "A Lie of the Mind"), he made a choice.

"I felt I had to make a decision, because I didn't think I would be taken seriously as a writer if I became a movie star," he says. "You don't want to be ignored as a writer because you have this other thing.

"There was a review of a play of mine in London a few years back that said, 'It's a pretty good play for a movie star.' And I thought, 'Ugh! This is exactly what I didn't want!' I also thought, 'Who does this motherf— think he is?!' But that's the trap you start falling into."

Still, Shepard has remained onscreen, doing supporting roles in films including "Black Hawk Down" and "The Assassination of Jesse James by the Coward Robert Ford" while new plays have gone up.

And though he splits his time between Kentucky and New Mexico, when he's in New York, he often sits in with his son's bluegrass band at Jalopy in Red Hook, and advises the experimental theater wing at NYU.

"It's surprising how many students are avidly interested in the theater," he says. "You'd think everyone would be interested in video or something.

"The difference between the '60s and now is that then, the theater was on the street. But to see that enthusiasm and energy is amazing."