I heard it was a girl, confined to her bed, in a hospital a long time ago. I believe I head that she had cancer, or another long-term disease. She used to lie in her bed at night and look out the window to the river, near the part where it emptied into the ocean. She could see the barges and hear their horns blow. She wrote the song, but died before she could finish. The story says that a girl scout finished the song, thus making it a Girl Scout tradition. But that was just at my camp, in the Bay Area in 1998. We didn't make up new, humurous versions because it was always kind of a sad, serious, and beautiful song for us. I cannot guarantee the authenticity of my version of the origin, but this is what I heard it was.
-Emily