What are some facts in the story "By the Waters Of Babylon" that show that the story is set in the future?

Stephen Vincent Benet uses fragmented or distorted names for what he hopes his readers will identify as places near and within New York City.  For example, John must cross a great river called the Ou-dis-sun by his people.  Benet wants the reader to realize, after the tale is ended, that he was referring to the Hudson River.  Since civilization was destroyed by a great fire (probably bombs, based on his description of John's dream), those who survived may have been affected by radiation or were injured in other ways, leaving them with possible speech impediments.  Over time, "Hudson" might have come out as "Ou-dis-son".  Also, broken buildings and statues from the bombs left fragments of names such as UBTREAS (for the Subtreasury Building) and ASHING beneath a statue of a man who "wore his hair tied back like a woman's" (George Washington).  References to what we call "modern" conveniences (indoor plumbing, elevators, stoves) seem like marvels to John, whose people were descendents of those who survived the blast and all the technology was lost.  All these examples point to the fact that this story takes place in the distant future after the destruction of civilization.