This year marks the centenary of the birth of Woody Guthrie, America's legendary singer-songwriter who roamed his land like a mediaeval troubadour, and whose work has comprehensively entered America's national songbook. Almost all Americans have at one time or another sung his most famous song, This Land is Your Land; it is virtually a second national anthem. Others to gain evergreen status include: So Long, It's Been Good to Know You, Union Maid, and Pastures of Plenty, to name just three.

Bob Dylan, Pete Seeger, Johnny Cash, Harry Belafonte, Joni Mitchell, Joan Baez, U2 and Billy Bragg have all sung his songs, which have also been adopted as state songs in two states. This Land is Your Land was sung by Bruce Springsteen and Woody's old friend and collaborator Pete Seeger at the 2009 inaugural concert for Barack Obama.

Guthrie's influence on generations of American musicians and songwriters has been enormous - not only in the relatively constricted domain of ''folk music'', but in country and popular music as well.

Yet his status as an iconic figure derives as much from his personality and lifestyle as it does from his influential music.

The legend has it thus: raised in a rural working class environment in the mythic American west, virtually untouched by modernity and popular culture, he sprang from the agrarian soil that many writers and artists have celebrated, even though few actually had such roots. Like a mediaeval troubadour Woody would roam and ramble the land, guitar in tow, singing for the poor, marginalised and the outcast. He sang the old ballads and work songs and hymns, or popular songs that had been absorbed into folk tradition. And he sang his own songs - compositions that were authentically ''of the People'', because he was. With his free roaming ways and his commitment to the common people, he was a living embodiment of the Declaration of Independence. And he did it all his way. He could not, he would not, be trampled, bought or sold - and he would get his message heard, whether through the mainstream media that were so resistant to it, or in defiance of them.

Such was the legend, and it remains so. As is ever the case with legendary figures, however, the human actuality was more complex and in some respects dissonant. He did come from the small western town of Okemah, in Oklahoma, but his family were not ''folk'' - not farm people or even manual labourers. His father made a tidy living by speculating in real estate, and was even elected to the position of District Court Clerk. But a series of adverse occurrences, including his mother's advancing infirmity due to a rare genetically transmitted disease known as Huntington's chorea, did bring hard times during Woody's adolescence, and he was given a first-hand education in the harsher realities of life faced by many Americans. Eventually, caught up in the swirling social uncertainties of the Great Depression, he often left the wife and three children he had acquired at a young age. He hitchhiked and rode the rails, supporting himself (and occasionally his family) as best he could through odd jobs and busking. The legend celebrates the rambling ways, but ignores the complicating domestic responsibilities that such youthful adventuring flouted.

It is true that Woody tended to be wary of allowing his musical talent to be bought and distorted to suit the aims of commercialism. But it is also true that he was willing at times to engage in some play-acting in order to cultivate popular appeal. Having drifted all the way west to Los Angeles, he found he could make a living with his playing and singing on the radio. A show that he co-hosted with a young woman artificially christened ''Lefty Lou'' for purposes of countrified authentication featured a lot of folksy talking by the smooth tongued Oklahoman, who was not averse to laying on the accent rather thickly and drawing upon the lexicon of slang in order to play to his fan base. For there quickly was a fan base: ''Woody and Lefty Lou'' became very popular among the uprooted agricultural labourers who were streaming into California in great numbers in those days, refugees from the terrible ''Dust Bowl'' conditions that years of drought had produced in the south and south-west. These people loved the songs on Woody's program because they were, or sounded like, old traditional country tunes seldom heard on the radio at the time. It was during this period that Woody began to write some of his own songs. His subjects were often familiar ones - love, country life, tragic deaths. But he also wrote about the experiences of the refugees who had abandoned their homes to come to California in response to promises of jobs only to find, like so many migrants before them, that conditions in the far west offered them little more than what they had left behind. Eventually these songs appeared in an album collection, Dust Bowl Ballads, that is now regarded as one of the milestone works in the history of American music.

During his years in Los Angeles Woody became a devout, albeit unorthodox, adherent of the Communist Party. For awhile he wrote a regular column in the party's newspaper, Peoples' World, and he sang for union meetings and at migrant worker camps. Eventually, though on the verge of even wider media success, he relocated to New York City, where his drifty ways, his songs of the people, and (not least) his dusty rural western accent impressed both folk music enthusiasts and young leftists - groups that overlapped considerably in those days. With Pete Seeger and several others he formed a group called the Almanac Singers, who lived a proto-hippie communal life in lower Manhattan writing protest songs and union anthems. The legend of Woody Guthrie highlights his leftist political orientation and his commitment, through his music, to the betterment of working-class and poor Americans. But his overt allegiance to the Communist Party is, at best, an optional inclusion.

Although the Almanacs regularly performed at union gatherings and at times on picket lines, they also did some national radio broadcasts, where Woody was the charismatic presence. Again popular success seemed to be his for the taking. He began to appear on his own on network shows, and for one, at least, he agreed to play down the leftist slant and perform the role of the affable, unthreatening country bumpkin. An offer to appear at a premier New York nightclub followed, and prompted him to turn away from the beckoning career path. When he was told at the nightclub audition that he would have to appear in a straw hat and do ''hayseed'' numbers he found himself again spurning widespread commercial success - and again hitting the road for a time.

But he returned to New York. A second marriage - to Marjorie Mazier, a dancer with the Martha Graham troupe - ensued, and the couple had four children. (One of whom, of course, Arlo, was later to become for awhile a more famous singer/songwriter than his father.) Though the legend fails to acknowledge it and few of his songs give hints, he spent many years in the metropolis, where his lifelong fascination with the written word flourished through contact with artists, social activists, and writers. He was by this time writing a lot about himself and his experiences, and in 1943 an autobiography, Bound for Glory, was published to favourable reviews. Much further effort was devoted to attempts at fiction, essays and memoirs; hours and days and weeks on end were spent before a typewriter. The People's folksinger was moonlighting as a New York writer - almost, one might say, a bohemian artist/intellectual. He continued to talk with the dusty drawl of a western farmhand and to cultivate that image as it suited him to do so. But few if any of the proletarians he tried to personify would have been, as he was, readers of Pushkin, Kahlil Gibran, Walt Whitman, or Karl Marx. A friend, a fellow Marxist from Oklahoma, told him to his face at one point: ''Woody, what on earth are you talking about? You never harvested a grape in your life. You're an intellectual, a poet - all this singin' about jackhammers, if you ever got within five feet of a jackhammer it'd knock you on your ass.''

It was a rebuke that Woody appreciated. But it did not stop him from enacting the role he was so good at, and that enabled him to create a rousingly self-conscious genre of modern ''folk song'' little dreamt of by the proletarian constituency he imagined he spoke for, much less folklorists.

The vast majority of Woody Guthrie's songs - and there were reputedly thousands - were forgettable, hence forgotten. The best of them, however, are masterpieces of modern so-called ''folk music''. His lyrics drew upon the common peoples' musical trove aggregated from centuries past; but they were infused with modernity in that they tilted leftward and looked upward. And they could be subtle and drily witty. Not only do they offer memorable images and wordplay, they also - in some instances - reveal levels of implication that make them worth listening to and pondering again and again. This Land is Your Land is a telling example. Few whose hearts have swelled in response to its vividly imaged praise of the nation's ''endless skyway'' are aware that it was initially conceived as an angry leftist response to Irving Berlin's saccharine anthem God Bless America. The title itself, which serves as the song's refrain, has a Marxist subtext: the land and all its resources belong - or should belong - to all the people, not just the rich and powerful. A verse in the original version conveyed the implication unmistakably: There was a big high wall there that tried to stop me/Sign was painted, it said private property/But on the back side it didn't say nothing/This land was made for you and me.

From early on that verse and two others in a similar vein have almost invariably been omitted from performances, omissions that have served to obscure the song's subversive gist. Ironically, it has therefore attracted parodies challenging its apparent refusal to acknowledge the nation's injustices. In the manuscript version, however, the song had pre-empted that response: In the squares of the city, In the shadow of a steeple; By the relief office, I'd seen my people. As they stood there hungry, I stood there asking, Is this land made for you and me?

Yet the tag line of the chorus turns the implicitly negative thrust of that rhetorical question on its head, prophesying hopefully that what will ultimately make the distressed nation as glorious as the land it inhabits is not a blessing from on high (as Irving Berlin's song had it); it is the will of the people, of the democratic masses, triumphantly audible in a voice that emanates from the grassroots, chanting: ''This land was made for you and me.''

Cruelly, as the music and the legend began to gain grassroots traction in the 1950s, the vitality of the real Woody Guthrie was on the wane. His behaviour, never predictable at the best of times, became increasingly erratic. He drank heavily, which was not unprecedented, but a growing tendency toward domestic violence was. After a series of misdiagnoses and frankly baffled responses from doctors it was determined that he was suffering - dying - from the same rare disease that had afflicted his mother. A serious accident with a fire brought on by his growing clumsiness left him badly scarred, and from that point onward he appeared to have surrendered to his fate. His last few years were spent in hospitals, where he became increasingly bedridden and insentient. By the end he was comatose, unable to speak or move any part of his body other than one finger.

The America of 2012 could do with a much heavier infusion of the music, vision and wit of its prodigal patriot Woody Guthrie, the self-styled ''Great Historical Bum'' who once wrote so slyly ''I like poor people because they'll come out winners in the long run. And I like rich people because they need friendship.'' May his spirit rest in peace - or roam and ramble thus, as indeed it might well prefer - once his likeminded compatriots finally manage to occupy Wall Street.

Woodrow Wilson (''Woody'') Guthrie: b. 1912, Okemah, Oklahoma; d. 1967, Brooklyn, New York.