In 1912, Daniel H. Burnham, the lead architect and Director of Works for the World’s Columbian Exposition of 1893, cruises with his family overseas on the Olympic, but is confined to his room much of the time because of physical ailments. He thinks of his good friend Frank Millet, who was the chief painter in Chicago’s World Fair of 1893, and who is also on a cruise ship: the Titanic. Burnham tries to send Millet a telegram, but the steward tells him that he cannot send it, because the ship Millet is on has been in an accident. Burnham does not worry because the Olympic is on its way to help.

In 1890, Chicago is rapidly changing and progressing. A young doctor, H. H. Holmes, steps off a train in Chicago, and he enjoys the city because of its smoke, chaos, and ability to hide dark acts. On February 24, 1890, Congress chooses Chicago to host the World’s Columbian Exposition of 1893, also known as the World’s Fair, and nicknamed the White City. Chicago wants to host the Fair to show New York and the rest of America that they can be a sophisticated city, despite their seedy reputation, and to upstage the 1889 World’s Fair in Paris. Burnham and his partner, John Root, are unofficially told they will design the Fair, as they are Chicago’s leading architects. Meanwhile, Holmes goes to a suburb of Chicago called Englewood and convinces Mrs. Holton to let him buy her drugstore, E.S. Holton Drugs. She mysteriously disappears.

Once Burnham and Root are given architectural control of the Fair, the board of directors argue for months about where to build it, cutting down on an already alarmingly short timeline. When the board appoints Burnham as chief of construction for the Fair, Burnham then employs Root as supervising architect. In 1891, Carter Henry Harrison loses his election for a fifth term as mayor. A young Irish immigrant named Patrick Prendergast campaigns for Harrison, and Harrison ends up winning the mayoral election of 1893.

At the end of October 1890, a recession begins. Holmes marries Myrta Belknap, and she works in his drugstore. He purchases a vacant lot across the street and plans to build a hotel for guests of the World’s Fair. The building is suspicious and includes vaults, gas jets, and a secret basement.

Burnham and Root slowly assemble a team of renowned architects, and begin planning their designs. They plan to build the Fair on the grounds of Jackson Park. Just after the architects begin work, Root dies. Burnham is crushed, but resolves to continue working on the Fair. The Fair faces many obstacles including arguing authoritative bodies, labor unrest, and the national recession. It progresses too slowly. While Burnham tirelessly supervises the construction, the Conner family rents a place in Holmes’ hotel building. Holmes has an affair with Julia Conner and tricks her husband, Ned, into buying the debt-ridden drugstore, prompting Julia and Ned’s divorce.

Julia Conner gets pregnant. Holmes convinces her to let him give her an abortion, but instead kills her and her young daughter, Pearl. Benjamin Pitezal introduces Holmes to Emeline Cigrand, and Holmes hires her as a secretary and courts her. Holmes suffocates Emeline in a gas-filled vault and sends her skeleton to Charles Chappell. Holmes finds a new secretary named Minnie Williams, whom he courts and then marries. He tricks Minnie into giving him her land inheritance.

The Dedication Ceremony for the Fair occurs at the end of October 1892, six months before Opening Day. The Fair is far from finished and damaged by weather and labor strikes. On his third attempt, a Pittsburgh engineer named George Ferris is finally approved to build the Ferris wheel as a rival to Paris’ Eiffel Tower. In January 1893, Olmsted’s protégé Harry Codman dies.

Exhibits arrive from around the world. Despite many more setbacks, Opening Day occurs on time, though some parts of the Fair are unfinished. Holmes begins to accept female guests into his hotel, and they start disappearing. The Fair builders finally erect the Ferris wheel and it is a success. Minnie’s sister Anna visits. Holmes takes them to the Fair and suggests that they vacation in Europe. However, on the morning they are set to leave, he kills both. Later, he meets his next wife, Georgiana Yoke.

Firemen die in a terrible fire at the Cold Storage Building because of construction flaw. Burnham and others are charged with criminal negligence, but everyone insists Burnham knew nothing about the flaw, and he is set free with just bail. Millet hosts a popular ball at the Midway to try and raise attendance; the Fair is in trouble of leaving the city in debt. However, on Chicago Day, the attendance is so high that it cancels the debt. Holmes escapes Chicago and runs away from the huge sums of money he owes. He goes to Minnie’s land in Texas to build a new castle. After learning that Harrison did not give him the job he wanted, Prendergast buys a gun and assassinates Harrison. Instead of a Closing Ceremony, there is a funeral and everyone says goodbye. The winter is harsh, homelessness explodes, and many Fair buildings burn the next year.

In June 1895, Detective Geyer searches for Benjamin Pitezal’s missing children. Holmes is in jail for insurance fraud, and claims he faked Pitezal’s death and the children are with Minnie Williams. Geyer tracks the children and finds all three of their bodies. Holmes is convicted and sentenced to a hanging. In the epilogue, the perspective switches back to Burnham on the Olympic. Burnham finds out that Millet was on the Titanic and has died. Burnham himself dies less than two months later.