(Nicki DeMarco/The Washington Post)

Sam Shepard’s plays never ambled. They rumbled and buckled and undulated, like patches of parched earth cracking open to allow hot gases to escape and scald everything in their paths.

His stage was always a space of exhilarating agitation, rife with evidence of blight and decay, often couched as a mourning for a disappeared American West and the pioneering spirit that once defined it. In “Curse of the Starving Class” (1978), the extinguishing of that spirit took the satirical form of a totemic kitchen appliance, a refrigerator that, no matter how many times the members of a benighted family opened it, was always bare. In “Fool for Love” (1983), set in a fleabag motel in the California desert, a cowboy tried vainly to win back the love of a woman who knows he’s destined to repeat the awful patterns of his alcoholic father. In “Tooth of Crime” (1972), an aging rocker engaged in musical combat with a fiery, presumptuous upstart — a battle reiterating one of the playwright’s favorite themes, that of an authentic America under siege.

He was himself an avatar of authenticity: a quintessential poet of off-Broadway, an instinctual writer whose earliest plays were born in converted (or actual) garages on the Lower East Side in the 1960s. Influenced by absurdist masters such as Samuel Beckett — “I think ‘Endgame’ is just a jewel,” he told me during a 1996 interview — Shepard became one himself, earning a Pulitzer Prize in 1979 for “Buried Child.” It will certainly go down as one of the great works of 20th-century drama, a scathing endgame for American values and emblematic of Shepard’s lifelong fascination with the harrowing fragility of family bonds.

Sam Shepard at the Hollywood Reporter Lounge at the Sundance Film Festival in Park City, Utah, in January 2014 . (Dan Steinberg/Invision/AP)

His death last week at age 73, from complications of amyotrophic lateral sclerosis, or Lou Gehrig’s disease, comes as a particular shock, not only because of his prolific output — he wrote nearly 50 plays, 30 of them produced before he was 30 — but also because his etched-in-granite profile was so recognizable. His in-demand acting career in film and TV owed more, I think, to his chiseled, Marlboro Man visage and seductive stoicism than to emotive depths, although his range of roles encompassed lyrical drama (“Days of Heaven”), comedy (“Baby Boom”), military thriller (“Black Hawk Down”), history (“The Right Stuff”) and romance (“The Notebook”). In a 2004 production at the New York Theatre Workshop of Caryl Churchill’s “A Number,” he looked stiff and uncomfortable; he acknowledged in an interview last year with the New York Times that theater was not his favorite mode for acting. “I find the whole situation of confronting an audience terrifying,” he told interviewer Alexis Soloski.

Which is kind of amusing, considering the fearlessness of his dramatic writing. He’s revered in theater circles for that bravery, for remaining true to his artistic voice and never being overly concerned with the commercial success of his plays. (Another reason his life as a movie star sometimes felt as if it belonged to another person entirely.) On Broadway, his work, more idiosyncratic and language-rich than driven by plot, had a hard time finding an audience; his biggest success was a 2000 revival of the raucous “True West” that ran for 154 performances, with Philip Seymour Hoffman and John C. Reilly playing brothers and each night, famously, switching roles. It would be another decade and a half before his work would be seen on Broadway again, in a revival of “Fool for Love” by the Manhattan Theatre Club.

“It’s not that I’m going to start writing plays for Broadway,” Shepard insisted to me back in ’96, just after a revival of “Buried Child” had opened to ecstatic reviews at the Brooks Atkinson Theater. (The play was revived again off-Broadway by the New Group last year, in a production with Ed Harris and Amy Madigan that moved to London.) He looked upon the opportunity to have a play produced uptown as a lark — he’d been done all over the world, of course — and was eager on this occasion to talk about his career and reveal that self-discovery was what he was after. Eschewing laptops, he said, he wrote in little notebooks, and the person he was most frequently drawn to putting into those notebooks was none other than Sam Shepard.

“In many of my plays, there was a kind of autobiographical character, in the form of a son or young man. The purpose of it was to write about myself,” Shepard said, adding that the character “was always the least fully realized.”

Enigmatic is often a word used to describe his most influential pieces. As the years went by, he sometimes departed from that wonderful mysteriousness and in more prosaic offerings, such as “The God of Hell” (2004) — a protest play responding to the Abu Ghraib torture scandal in Iraq — resorted to agitprop. Maybe he’d lost patience as he grew older, for one was more accustomed on an evening with Shepard to have one’s expectations exploded, not confirmed. When you ventured into Shepard’s darkness, you were joyfully encountering an artist groping for the truth in the thickest mists.