Rowling was 25 years old when she came up with the idea for "Harry Potter" during a delayed four-hour train ride in 1990.

She started writing the first book that evening, but it took her years to actually finish it. While working as a secretary for the London office of Amnesty International, Rowling was fired for daydreaming too much about "Harry Potter," and her severance check would help her focus on writing for the next few years.

During these years, she got married, had a daughter, got divorced, and was diagnosed with clinical depression before finally finishing the book in 1995. It was published in 1997.