Fifty years ago today, "The Plow That Broke the Plains," a short documentary about the Dust Bowl, had its Washington premiere at the Mayflower Hotel. It is now considered one of the most influential U.S. documentaries ever made, but at the time detractors called it propaganda for the New Deal. Hollywood's moral arbiter -- the Hays Office -- even tried to block its distribution.

Tonight the Washington Film Council will mark the event with showings of "Plow" and "The River" (a 1937 film about the erosion of land around the Mississippi) at American University's Wechsler Theater. The filmmaker, 80-year-old Pare Lorentz, will be there.

On a budget ultimately just shy of $20,000, Lorentz took a handful of notes to selected locations in the Great Plains, and set photographers Paul Strand, Leo Hurwitz and Ralph Steiner to work. The result is a series of compelling images of grim-faced farmers valiantly (but foolishly, it is argued) churning the earth into so much desert; of overlapping dust dunes receding into the distance; of migrants looking for new land.

The film has lost none of the emotional drive, which is powered by Virgil Thomson's musical score and the booming voice-of-God narration of Thomas Chalmers (a former Metropolitan Opera singer and That Voice on the March of Time newsreels).

"Nothing to stay for, nothing to hope for," intones Chalmers as we see concluding footage of bereft farmers driving to migrant camps. "Homeless, penniless and bewildered, they joined the great army of the highway -- no place to go, no place to stop . . . "

Lorentz's impression of a man-made desert didn't sit well with the interested parties of the time. In South Dakota, for example, Republican State Chairman Harlan Bushfield said that Lorentz "in one savage blow ruthlessly destroyed all that South Dakotans have have built up in a generation," by "picturing the state as a wasteland." Lorentz remembers a telegram from Kansas that said, " 'We have no drought and, besides, we have the largest outdoor swimming pool in Kansas.' "

In "The River," cameramen Willard Van Dyke and Floyd Crosby (among others) filmed various points of the river and its tributaries and had the chance to film some massive flooding. Lorentz, who had anticipated resorting to stock clips for floods, now had spectacular original footage of man battling the water.

" 'The River' is in every way more powerful than "Plow" ," says Lorentz. "We had the blessing of the White House. The words are better . . . the floods came out. I was born and raised in West Virginia, so I knew about lost land" from flooding.

Lorentz's narrative script, which was published in full in McCall's magazine, is often extensively quoted in film anthology books.

"Plow" and "River" became issues in the Capitol Hill battle over government film appropriations. And the U.S. Film Service, which Lorentz headed, died an early death. Lorentz, who had been a film critic at McCall's before making the two documentaries, became the magazine's national-defense editor. He spends much of his time now lecturing on his films and talking with "the new generation."

Many of the people who worked with Lorentz have since died, he says, but Thomson is still around, he says, and "will be celebrating his 90th birthday, and every time I'm supposed to put up some money for some revival of his work."

Lorentz is completing a revised edition of his collection of film critiques, called "Lorentz on Film." There is also an autobiography pending, which he says he started when he was 12.