I think there’s a version of this song with the last verse in a minor key. Johnny Cash’s version has the major key in every verse but Allan Sherman’s parody “The Streets of Miami” has the minor-key last verse.
Can you point me to a non-parody performance of the song that has the minor-key last verse?
Hmm. I know that Theodore Bikel sang a very strange minor key bit of streets of Laredo when he appeared on Gunsmoke, but that’s only because MeTV has been running it in promos.
Sorry, I couldn’t resist looking this up on the very first LP I listened to … a live Kingston Trio album with a song called “Laredo?” (Live at UCLA, '61).