- The cryptic property is:
the date of statehood (the date of admission to the union).
http://en.wikipedia.org/wiki/List_of_U.S._states_by_date_of_admission_to_the_Union
The list has the statehood dates ordered upside down: the younger states come at the beginning, the later states come at the end
- The first missing state is:
Nebraska (admission date = March 1, 1867).
- The second missing state is:
Mississippi (admission date = December 10, 1817).
