It's what happened in
America in the '20s
Take a Tour of Josie's New York
Most of the places described in the book are much as they were in 1929. 
These are some of the buildings that Josie spent time in and which are still open to the public, 
so you can plan your own walking tour.

Cartier Building since 1917
The famous New York Location at 653 Fifth Avenue and Cartier Place was formerly the Neo-Renaissance mansion of Morton Freeman Plant, son of railroad tycoon Henry B. Plant and designed by architect C.P.H. Gilbert. Cartier acquired the mansion from the Plants in exchange for $100 in cash and a double-stranded natural pearl necklace valued at the time at $1 million.
See Wikipedia

Bergdorf Goodman's
Fifth Avenue entrance of the downtown Manhattan department store built in 1928 in the Art Deco style. Until 1927, the entire block where this department store is located and buildings behind was the Cornelius and Alice Vanderbilt mansion. Josie and her friends had attended numerous parties at the Vanderbilt home but later shopped at the upmarket store.
The House of Morgan
Headquarters of the Morgan bank during the Stock Market Crash and location in 1929 AN UPPER CLASS AFFAIR, where Josie goes to meet Jack Morgan in his office, after the crash. Readers today can still walk past this famous building which is very close to the NYSE.

St. Bartholomew's Church
on Park Avenue, the scene of many society weddings that Josie attends
Central Park
Josie lives across from Central Park and often strolls within it alone and with Charles.

Harry Winston
The ornate iron and glass doors were typical of the elaborate architecture displayed in 5th Avenue townhouses of the rich when Josie was growing up in New York. Currently the townhouse is the flagship store for Harry Winston Jewelers.
Plaza Hotel
Opened October 1, 1907 with great fanfare from the upper classes, a number of whom took spacious apartments for themselves in the hotel. During the 1920's, the Plaza's tearoom, ballroom, and all male brokerage were frequented regularly by New York's elites. Today, the hotel still offers afternoon tea and its ballrooms for anyone who can pay.

James B. Duke Mansion
Now NYU's Fine Arts Institute at East 78th Street and 5th Avenue. This is Josie's family's townhouse in the novel and where I wrote some of the book.
Trinity Church
Also known as Trinity Wall Street, it is an Episcopal church located at 79 Broadway and the corner of Wall Street. The church received its charter from King William III in 1797 and has continued operating as a functioning parish since that time. The current structure was built in 1846 and has 23 bells, bronze doors by Richard Morris Hunt and beautiful stained glass windows. Some of the most famous New Yorkers are buried in its graveyard including Alexander Hamilton, Robert Fulton and William Bradford. In 1929 AN UPPER CLASS AFFAIR, Charles, along with numerous investors, sought solace within the church during the Great Stock Market Crash.