In a nation whose popular music has been shaped and defined by the shiftless nature of its people, Nelson is the ultimate hobo. Born in 1933, north of Waco in Texas, in a cotton-farming town called Abbott that doesn't even exist any more, Nelson has barely stopped moving since.
Abbott was the kind of town built for escaping from. Around the time Nelson was born - at the height of the Depression - it looked like a B western, the scene where the tumbleweed blows down the dusty main street and the camera zooms in on the old town limits sign: "population 300", carved into a lopsided battered board.
But unlike thousands of other performers emerging from backwoods beginnings, Nelson is no country cornball, no Wild West cliche. His father was a travelling mechanic; his mother went looking for work one day and never returned; so Nelson was raised by grandparents with an eclectic record collection, including Sinatra and jazz as well as popular Western swing artists such as Ernest Tubb and Bob Wills.
These varying influences were not lost on Nelson, which is probably why he has always managed to appeal to audiences for whom the words "country" and "western" in any kind of proximity are normally anathema. Nelson's jazz phrasing is as distinctive an element of his music as the melancholic autumnal voice that can render the most banal material deeply affecting. In the twilight glow I see her/ Blue eyes crying in the rain/ When we said goodbye and parted/ I knew we'd never meet again. This fairly unremarkable opening stanza from one of Willie Nelson's greatest hits is elevated by his performance into a kind of truck-stop poetry.
Perhaps it is because he is singing about what he knows. For 40 years, carrying the same battered guitar, Nelson has criss-crossed his homeland. The Willie Nelson website describes him as "a highwayman, a sad, spiritual poet endlessly travelling America, his voice as cracked and weather-beaten as the well worn leather skin that clings to his frame. He doesn't want to stop. Probably can't."
But if Nelson had merely carried on until retirement age performing more or less the same act, he would probably earn nothing but our scorn. He has in fact continually renewed his artistic vision. His albums, which number more than 100 - some estimates put the figure as high as 200 - draw deeply on pretty well every strand in American popular music.
Nelson's endless striving for something new has no doubt played a part in his chequered romantic history - four times married - and his experiments with various drugs alongside his beloved whisky.
The affection felt for Nelson by his compatriots crosses not just musical divides but social and political borders as well. He understands redneck culture, yet behaves like a hippy. He regularly joins family farmers to campaign against factory farming. Some idea of the support Nelson commands became apparent when he was landed with a $16m claim for back taxes. His defence - "I forgot" - was in fact quite convincing, coming from Nelson, and when he was forced by the IRS to sell his possessions, the purchasers returned them to him.
But Nelson was far from being a tax-dodging pariah; his contemporaries beat a path to his door to record with him - Ray Charles, Bob Dylan, Neil Young and others - while the man himself continues to get his kicks on Route 66 and wherever the muse takes him.