Which Harry Potter novel was the first to sell more than one million copies in its first 24 hours in the United States?

Harry Potter and the Goblet of Fire was the first Harry Potter novel to sell more than one million copies in its first 24 hours in the United States.

Published in 2000, Goblet of Fire was the fourth book in Rowling’s series. It is substantially longer than the earlier novels and expands the story beyond Hogwarts through the Triwizard Tournament, an international magical competition involving three schools.

The book’s American first-day sales were reported at about three million copies, a remarkable publishing event that demonstrated the series’ enormous commercial growth. The figure is often confused with later records set by the fifth, sixth, and seventh books, which also achieved extraordinary opening sales.

The novel is important narratively because Voldemort returns to a physical form near its conclusion. That event changes the series from a school-centered adventure into an open conflict involving the wider wizarding world.