In both "El Paso" and in the separate song "El Paso City" - both written by Marty Robbins - he references the New Mexico badlands.

I've never heard "El Paso City" (seen the words) and in it he talks about flying 30,000 feet above it. Really threw me for a loop, headwise, because I kept thinking - "there's no stinking aeroplane in the song 'El Paso' !!!" Now it all makes sense.