The Age Of Innocence, Edith Wharton, Norton Critical Editions -- c. 2003

Age of Innocence, Edith Wharton, 1920.

Wiki.

For context,  

The Great Gatsby, 1925.

Virginia Woolf:
The Voyage Out, 1915, age 31:
Mrs Dalloway, 1925,
To the Lighthhouse, 1927

Wharton said the book took place during the decade, 1875 to 1885 (the US Civil War had ended 1865).

Analysis of her novel suggests the "decade" began in 1870 and extended to the mid-1880s.

The story of NYC's two opera houses. -- page 3 in footnote #3.

• Academy of Music.
• Vanderbilts couldn't get a box seat.
• Metropolitan Opera House: opened, 1881.
• Built by Vanderbilt.

So, the timing makes sense. The book opens with references to "talk" of a new opera house “above the Forties" -- so, in 1870, there was no "new" opera house yet.