Woody Guthrie scribbled the words to "This Land Is Your Land" down on a loose-leaf sheet of paper in 1940. He recorded it for Moses Asch, founder of Folkways Records, in 1944, but the song wasn’t released until 1951. By that time, "This Land Is Your Land" had become something of a leftist national anthem.
http://www.npr.org/2000/07/03/1076186/this-land-is-your-land