Plus some info:
[1996:] Mostly this song was written to the memory of Woody Guthrie. I first heard an album of Woody's back in about 1957 and from the very first bar of "Columbus Stockade" I was hooked. I had no idea of how famous the man might be in America and chanced a letter addressed to Woody Guthrie, USA. I waited with baited [sic!] breath for six weeks, but the letter came back "insufficiently addressed". A year or two later, I found out that Woody was in hospital in New Jersey with an incurable wasting disease and started writing to him there. He was physically unable to write back but Bob and Sidsel Gleason, who would take them to their home for weekends at that time, wrote and told me how he was and passed on answers from Woody to my questions.
When (Ramblin') Jack Elliott came to London, I was too shy to approach him after his gig at the Ballads and Blues Club, but followed him and his wife home on the Underground till I saw them go into 11 Kensington Park Road. I wrote to him and he rang me and said come on over. I didn't just go over, I more or less moved in! What a plague I must have been, but they didn't seem to mind. Jack showed me how to play the 'Mouth Harp' upside down and the 'Cross Harp' style, same as Woody had shown him, told me stories about him and Woody, and changed my life.
Somewhere, to this day, I have an issue of the "Woody Guthrie Newsletter" which starts - "Woody would like to thank ...". There follows an inventory of the American folk heroes of the day, Pete Seeger, etc. Most of the page is taken up with these names and I suppose, when I first read it, I was hoping against hope that I might be there too ... But, of course, no ... But wait? Right at the bottom I read: "And to Andy from Woody personally". I never tired of the road since. (Notes Andy Irvine, 'Rain on the Roof')

Also, there's an article on Woody Guthrie on the Mudcat, accessible via the front page (but not tonight, it seems).