One evening about three years ago, I played "Streets" in a summer camp dining hall open stage to maybe 300 adult "folkies". That audience all knew the song and sang the choruses along with me. I was nervous, and mid-song I forgot the chords. I stopped playing but kept singing. So did the audience. We finished together, and everyone gave themselves a round of applause. Later someone thanked me for "ending the song that way, and giving us an chance to sing"

So it's a folk song.