Kingman, Barstow, San Bernardino.
I wondered why Bobby Troup crafted the names of those last three towns in a descending musical scale, and then found out why: each town is (roughly) 1,000 feet lower in elevation in the order named as you travel west.
He was married to Julie London so he cannot be questioned. Jack Webb however can be :)
The drops are more easily seen from Flagstaff (7400 ft.) down to Kingman.