In an article in the February 1974 Word Ways, Dmitri Borgmann nominated Zzyzx Springs as the alphabetically-last United States place name. THis name apparently is in no gazetteer (even the comprehensive Ran McNally Commercial Atlas and Marketing Guide); he cites as his source an undated map published by the Automobile Club of Southern California, covering San Bernardino County. He characterized it as
Eckler, A. Ross
Word Ways: Vol. 29
, Article 10.
Available at: https://digitalcommons.butler.edu/wordways/vol29/iss1/10