Indy and his father are taking spring vacation in New York City to visit "Aunt" Mary. As the book opens, Professor Jones is doing research in New Haven, CT at the Yale University Library for a paper he's writing on the Normans. The Normans were the inhabitants of the Duchy of Normandy (in northern France), descendants of the Norse Vikings who went on to invade and conquer several areas of Europe and England.

On page 10, Indy visits Union Square, a neighborhood in the Manhattan borough of New York City.

On page 11, Indy sees a protest for women's suffrage and is fascinated, having heard about women fighting for the right to vote, but they hadn't seemed quite real until now, right in front of him. But he'd already experienced a bit of the English suffrage movement in The Titanic Adventure. 

On page 17, Lizzie swats away a thug with her closed umbrella, saying, "That's Dr. Latson's method of women's self-defense." Dr. William Richard Cunningham Latson (1866–1911) was an American physician, occultist, and self-defense expert. In 1906, a series of photo illustrations depicting "Dr. Latson's Method of Self Defense" was produced, including one of a woman defending herself with an umbrella.

On pages 21-22, Indy and Lizzie talk about her recent attendance to Georgetown University in Washington D.C. and transfer to Barnard College in New York City. As stated in the novel, Barnard College is a women's college of Columbia University.

On page 22, Lizzie reveals she has joined the Congressional Union. This was a real world suffragette organization in the United States from 1913 to 1916.

Roberto tells Indy and Lizzie he is from Sicily. He is staying with his aunt and uncle and their lodgers at an apartment in Greenwich Village on Thompson Street south of Washington Square. Greenwich Village is currently an upper middle class residential neighborhood in lower Manhattan, but in 1914 was more lower class and is known for its Italian immigrant population. Thompson Street and Washington Square are both parts of Greenwich Village.

On page 28, the Italian lodgers tell their story of coming to the U.S. in the steerage of a ship and how they were kept on Ellis Island in a pen for a time when they arrived while authorities decided on whether they could stay. Ellis Island was a famous gateway to the United States for millions of immigrants from 1892-1954.

On page 29, Roberto talks about the Brooklyn Dodgers and the New York Giants. These are both Major League Baseball teams, though the Dodgers transferred to Los Angeles in 1958.

On pages 40-41, Professor Jones seems surprised to hear that women don't already have the universal right to vote in the United States. As Mary points out here, women did have the right to vote in Utah (where the Prof and Indy lived at the time) in local elections, but not nationally. But the Jones boys had lived in New Jersey about a year before they moved to Utah (after the death of Mrs. Jones) and women did not have suffrage in New Jersey, so the Professor should already be aware.

In Chapter 5, Indy meets Lizzie in front of the luxurious Plaza Hotel on Fifth Avenue. The hotel opened in 1907.

On page 44, Indy sees a Rolls-Royce automobile parked in front of the hotel.

During their meeting at the hotel, Indy wears the straw skimmer hat Lizzie gave him at the end of The Plantation Treasure.

On page 45, Lizzie wonders, in regards to women's fashions, how women can let themselves be slaves to some Paris designer. Paris, of course, is known as one of the four (possibly the first) capitols of fashion in the world.

On page 47, Lizzie tells Indy that her friend Minna's parents perished on the Titanic and Indy "recalls" that the ship sank when it hit an iceberg in 1912. He doesn't seem to "recall" that he was on the Titanic when it happened (in The Titanic Adventure)!

The dean of Barnard College is said here to be a woman named Sayers. The college has not had a dean by that name in actual history. In 1914, the dean was Virginia Gildersleeve.

On page 54, Professor Jones and Dean Sayers become engrossed in talking about the dean's collection of old books such as the Rerum Italicarum Scriptores, Geoffrey de Malaterra's Historia Sicula, and the Amatus of Monte Cassino's Yistore de li Normant. These are all real books about the histories of Italy and Sicily, hundreds of years old.

On page 56, Roberto walks through the construction site with a stone block on either shoulder, looking like a statue of Hercules come to life. Hercules was the Roman name for the Greek hero/demigod Heracles.

On page 66, Roberto refers to his family's heirloom as Il Croce Ruggiero, implying it means "Ruby Cross" in Italian. Croce does mean "cross", but, as Indy realizes Il Croce Ruggiero actually means "The Cross of Roger" (Count Roger I of Sicily as Indy eventually realizes).

On page 75, Roberto relates that there is a curse on the Cross, that anyone who steals it will die, and that whoever loses it is also cursed. Lizzie jokingly asks if the loser gets a seven-year itch. "Seven-year itch" is another name for scabies, an infestation of the skin by the mite Sarcoptes scabiei. The name comes from the fact that mite infestations tend to occur in roughly 7-year cycles. (Regarding the Cross' curse, Roberto answers Lizzie that the loser of the Cross will die as well.)

In Chapter 9, Indy masquerades as a Western Union messenger boy in order to talk to Minna Frobisher.

On page 80 Wilfrid Frobisher remarks that all the "big fellows", like Rockefeller and Astor, are bidding on the ruby cross he's acquired. The Rockefeller and Astor families were prominent business moguls in America and among the wealthiest in the world at the time. The Rockefeller mentioned here is probably John D. Rockefeller Jr. (1874-1960) since Indy mentions that Rockefeller is known as a collector of medieval art and relics. (Indy also goes on to say that Rockefeller occasionally has his father advise him on the Middle Ages!)

On page 80, Wilfrid calls the operator to dial up Murray Hill 3467. Murray Hill is an affluent neighborhood of Manhattan.

The information Indy relates about the Norman participation in the Crusades, a kingdom at Antioch, Robert de Hauteville, and Roger de Hauteville's conquering of Sicily on page 91 is accurate. Roger is not, however, said to have a cursed magic sword historically as he apparently had here (this is also mentioned in the Historical Notes at the end of the book).

On page 95, Indy follows Roberto onto the train at the Ninth Street and Sixth Avenue station. This is an actual rapid transit station in Greenwich Village.

On page 103, to contradict Lizzie's skepticism about Roberto's magic cross, Indy mentions that since their last adventure together the previous year (in The Plantation Treasure), he's bumped into a magic crown, two magic rings, and magic fire. He's referring to his adventures in Tomb of Terror, Princess of Peril, The Ghostly Riders, and Circle of Death.

On page 104, Indy whistles "She's Only a Bird in a Gilded Cage" as he and Lizzie stroll past Minna's mansion home as part of a signal to Minna. This refers to "A Bird in a Gilded Cage", a 1900 song by Arthur J. Lamb and Harry Von Tilzer.

In Chapters 11 and 12, Wilfrid's auction for the Ruby Cross takes place in a private dining room at Delmonico's. Delmonico's was a restaurant in Manhattan at the time, famed as one of the best fine dining establishment's in the nation. It closed in 1923, although a new Delmonico's exists in the original building now.

On page 108, a man named Amory tries to tell Wilfrid he should try a new health cereal his company is coming out with, a new wheat flake. I've been unable to determine if Amory was a real world entrepreneur, nor if there was a new brand of healthy wheat flakes cereal coming out around 1914 (Wheaties came out in 1924).

On page 111, Indy shouts "Veni, Rogere, veni!" to activate the magic of the Ruby Cross. This is Latin for "Come, Roger, come!"

As the ghost of Count Roger I of Sicily is about to slice Wilfrid's throat with the sword on page 114, Indy shouts, "Ne iugula!" This is Latin for "Not his throat!"