Kayce wanted to rejoin the Navy SEALS. His former Commanding Officer asked him "You're not a year from discharge?". The rationale behind the question being, based on the period of time of his "break in service", he would be required to attend mandatory training and observe other formalities before he can be placed on "active duty".
As stated by John to Tate, the central part of the United States did have a vast inland sea nearly 115 million years ago, the Arctic Ocean had begun to flood the basin from the north, and by around 100 million years ago, that was called the Western Interior Seaway (WIS), was formed. The Western Interior Seaway was a continuous seaway extending from the Arctic Ocean to the Gulf of Mexico. The Western Interior Seaway lasted for about 60 million years, longer than the human species, which came to an end around 70 million years ago. Climate change likely dried up the interior seaway and held its waters frozen in the poles. Moreover, further tectonic activity caused the WIS to experience multiple fluctuations in sea-level. Eventually, the seaway closed off at the end of the Cretaceous period and gradually disappeared due to regional uplift and mountain-building on the western side of North America. Today people visiting the Great Plains can still see the remains of this prehistoric sea. In much more recent history at the end of the last ice age, North America once had a massive inland lake that was larger than the combined Great Lakes today (called Lake Agassiz)
According to the tombstone marker, Evelyn Dutton died on March 30, 1997. The circumstances of her death are addressed in No Good Horses (2018).