In his first column as Kickshaws editor in Feb. 1989, Dave Morice showed how one can construct chains of state names using thier postal codes: Maine contains IN, the postal code for Indiana; Indiana contains IA, the postal code for Iowa; Iowa contains WA, the postal code for Washington, and so on. More generally, one can construct a directed network of state names containing a core of states, any one of which can reach any other (AK AL LA IA WA IN ND AND HI), starter states which can be chained to the core but which cannot themselves be reached (for example, Pennsylvania or Minnesota), and ender states which can be reached from the core but which cannot generate a successor (for example, Kansas from Alaska or Massachusetts from Alabama).
Eckler, A. Ross
Word Ways: Vol. 44
, Article 4.
Available at: https://digitalcommons.butler.edu/wordways/vol44/iss4/4