Hallelujah, praise the Lord, Wise Blood is out on DVD. John Huston's hellfire burlesque is one of the great lost films of the 1970s and a movie to stand alongside his Maltese Falcon or The Treasure of the Sierra Madre. I first blundered across the thing as a teenager, stumbling blind around the late-night TV schedules. Last night I paid a return trip and was reassured (I hesitate to say relieved) to find it just as rich, dark and flat-out weird as it was before.

Adapted (pretty faithfully) from the novel by Flannery O'Connor, Wise Blood charts the efforts of a wild-eyed young preacher to establish a new religion. Rattling around a depressed southern town, antsy Hazel Motes (Brad Dourif) preaches the gospel of "the Church of Christ Without Christ - where the blind can't see, the lame don't walk and the dead stay that way".

But Motes possesses an achilles heel. He is at least half in love with what he professes to hate, affecting the outfit and the speech of a Pentecostal Bible-basher even as he urges his flock to throw off their shackles and shrug off their sins. "Nothing matters but that Jesus was a liar," he harangues them from the bonnet of his car. "I ain't saying that he weren't crucified, but it weren't for you."

Huston (credited here as "Jonh Huston") was 72 when he shot Wise Blood – a Hollywood lion in his dotage. You'd never guess. Wise Blood feels like a first film: energetic, unrefined and a little off-kilter, as though the director was tussling with his material; slightly flying by the seat of his pants.

And yet for all its berserk gestures and grotesque inhabitants, the end product proves utterly convincing. Wise Blood is funny, sad and thought-provoking. It is brilliantly played by a cast of left-field character actors (Dourif, Ned Beatty, William Hickey, Harry Dean Stanton). It may also be the film that best captures a particularly American strain of craziness - spotlighting a southern subculture where shifty men peddle Jesus on street corners and lonesome kids go quietly insane at the local zoo. At times, in fact, the film is so peculiarly, locally, pure-bloodedly American that it turns almost otherworldly - as exotic to our eyes as some arcane arthouse delicacy, blown in from Eritrea or the Kazakh steppes. We don't know quite why these characters are doing what they're doing, exactly, but we believe them just the same.

Wise Blood is finally released on DVD in the UK on 2 March. It is the film that was lost and now it is found, and for that we should be thankful. But why has it taken so long? It's not as though Huston is an obscure film-maker, or that the 70s American film scene has been starved of attention in recent years. Perhaps it simply goes to show that, even the most well-mapped, well-settled landscape, there are still some dark corners to hide away.

When setting out the landmarks of 70s American cinema, we inevitably namecheck the usual suspects: Badlands, Nashville, Taxi Driver, The Last Picture Show, Chinatown, etc. And fair enough: they're all great films. But the more light we shine on the anointed few, the more we risk blinding ourselves to the others, to films that are arguably just as interesting, ambitious and unusual but which have been left to languish in the shadows. Films like Wise Blood, say, or The Hired Hand, They Might Be Giants, Cockfighter, Smile or The King of Marvin Gardens.

Hapless Hazel Motes tries to bury Jesus but can't, because Jesus will not be denied. He is "the ragged beggar, darting from tree to tree in his mind". Wise Blood is a bit like that too, and chances are it's not alone. What other great forgotten films are still out there in the woods, ragged but alive; waiting for us to track them down and bring them home?