If you use proper grammar, you Capitalize Proper Nouns. The corner is a place, it doesn't need to be capitalized, but Mount Rushmore is a place, and it does need to be Capitalized because Mount Rushmore is a proper noun.
In the Unknown Citizen, Auden is using Press, Union and Public Opinion as proper nouns. The Press is a specific person in the story (i.e. a proper noun). The Union is another specific person (i.e. a proper noun).
Why he makes these proper nouns, relates to the message he is trying to illustrate with the story. I hope that helps you understand his marriage.
To sustain any sort of credibility on this website, this inane and entirely nonsensical answer should be reviewed