Jealousy and Regret: The Banks of the Ohio

"The Banks of the Ohio" (Roud 157) is a pretty straightforward song as far as these things go, and, as is often the case with these simpler old songs, its history is nearly impossible to trace. What I can tell is that it showed up in the United States sometime in the late 1800s, and was first recorded in the late 1920s. Beyond that, I haven't come across a direct ancestor in European folklore (though the theme of drowning someone out of romantic jealousy is pretty common), so I'm guessing it's an American original.
The story is simple: the guy ("Willie" in many versions) is in love with a girl who likes him at least enough to walk out with him. He wants her to marry him, she's not into it, so he drowns her and then feels bad about it.

It's been performed and recorded a lot, it's an easy song to play (when one isn't fumbling the F chords because your hand is sore) and the chorus makes for a nice sing-along, it's also been made into at least one delightful web comic adaptation.

Perhaps the distinguishing feature about "The Banks of the Ohio" is the theme of regret. After the murder, the narrator laments how he killed the woman he supposedly loved. There are a number of songs about jealous lovers or competing suitors killing someone in a fit of passion, but usually, if there's any aftermath it's either treated as a moment of grotesque justice as in "Mattie Groves" or something they hide until they get caught as in "The Cruel Sister," whereas our narrator has a moment to realize that losing his temper and drowning a woman was A TERRIBLE IDEA.

I mean, it shouldn't take even a three-and-a-half minute folk song to figure that out, but we live and we learn, right?