From a TPM post on the death of Pete Seeger ...
Guthrie, a complicated and tragic figure, was one of those folk icons who genuinely appeared to rise up out of the earth from nowhere, born into a sort of boomtown prosperity which was soon shattered by financial disaster, maternal loss, insanity and profound poverty. Seeger was blessed with good genes (his father lived to 92, he to 94), born to a Harvard-educated academic. They were completely different sorts of people and yet connected up in this channel of folk music and radicalism.
He is best known as the writer of "This Land is Your Land" (1940), written as a counter national anthem, fueled by disgust with what he perceived as a complacency and unrealism of "God Bless America", then a staple of American radio.
In his mid-30s, Guthrie began to show the signs of what would later be diagnosed as Huntington's Disease, a progressive and fatal neurodegenerative disorder. He died, aged 55, in 1967.