BOOK REVIEW : Southwestern Subculture Survives Depression : AMERICAN EXODUS: The Dust Bowl Migration and Okie Culture in California <i> by James N. Gregory</i> Oxford University Press $24.95, 338 pages

Dorothea Lange’s haunting photograph of a careworn young woman holding a sleeping baby, titled “Migrant Mother,” is one of the icons of American culture, a back-road Pieta that symbolizes the ordeal of the refugees who fled the Dust Bowl of Oklahoma and Arkansas to seek their fortunes in California in the 1930s.

At the very outset of “American Exodus,” historian James N. Gregory shatters our assumptions about the famous photograph by giving us another view of the same scene. Instead of a tight close-up of mother and baby, the photographer has stepped back to show us the ragged tent-half that shelters the family, the big black suitcases that hold their possessions, the trash that litters the sandy soil of a pea field near San Luis Obispo, and the face of a distraught child who watches the camera. Suddenly, art turns into history.

For me, Gregory’s gloss on a primal image of the Dust Bowl saga is a good example of what he has accomplished in “American Exodus.” The author steps back from the tragic grandeur of Steinbeck’s “Grapes of Wrath” and the poignant folk-poetry of Woody Guthrie’s “So Long (It’s Been Good to Know You)” to reveal the commonplace but telling details of the “heartland exodus” that he calls “one of the most important and least understood demographic events of the recent past.”

“Even before John Steinbeck translated the experience into one of the classic American novels of the 20th Century, the migration had become a media event,” Gregory writes. “But there is a deeper story to be told about the same people.”

The story that Gregory tells in “American Exodus”--”the ways American culture is transformed through population movement”--is drawn from the source materials of history. He gives us first-person recollections of the “Okies,” including the families of Merle Haggard and Buck Owens; headlines from the Los Angeles Times and fragments of poetry from the mimeographed newspapers of the work camps; songs, billboards, graffiti and Hollywood movies that depict the plight of the “Okies” as well as a generous collection of charts, graphs and maps that tell the same story in statistics.

“American Exodus” looks beyond the Dust Bowl era to contemporary California, where Gregory has detected an “Okie subculture” that survives in Bakersfield, Fresno, Modesto, Merced, and throughout the San Joaquin Valley. Indeed, the basic theme of “American Exodus” is the persistence of a kind of gritty folk identity even under the millstones of urbanization, mass media and popular culture. And his final chapters--”Special to God” and “The Language of a Subculture”--are an eloquent summing-up of the “Okie” experience in America as expressed in its most visible and enduring legacies, religion and music.

“One needs only be within radio range of the Southern San Joaquin Valley today to hear the Southwestern influence,” Gregory writes. “Here are the most distinctive public voices of the Okie subculture--the drawling heart-of-America songs of the country-Western idiom and the soul-saving preaching of evangelical Protestantism. Separated by only a few megahertz, they are the twin keys to the dynamic influence of Southwesterners in California.”

S outhwesterner is the deferential label that Gregory puts on the people who were once called “Okies” or “Arkies,” and, indeed, the author is sensitive to the slurs and stereotypes that once afflicted them.

“As late as 1949,” he reports, “the Yuba County school system classified the accent of children from Southwestern backgrounds as a ‘speech defect.’ ”

Even Steinbeck, he insists, “crafted a portrait that many former Dust Bowl migrants have long regarded as demeaning.” Says one “Okie” woman about the author of “Grapes of Wrath”: “(I) spent a lot of years hating him.”

The bulk of “American Exodus” consists of social history in a rather technical sense. Almost a third of the book is given over to appendixes, annotations, and indexes. But Gregory has poured his heart into his work, and what might have been a dry loaf is leavened by his unmistakable sympathy for his sources and his subject matter. As Gregory concludes:

“Okies are people who have known suffering, who are tough enough to rise above it, who can be guilty of redneck intolerance, even as they never forget the ‘essentials,’ namely, that ordinary folk are the guts and sinew of American society.”

Next: Richard Eder on Michelle Latiolais, “Even Now” (Farrar, Straus & Giroux).