Hillenbrand's first book was the acclaimed Seabiscuit: An American Legend , a nonfiction account of the career of the great racehorse Seabiscuit, for which she won the William Hill Sports Book of the Year in 2001. She says she was compelled to tell the story because she "found fascinating people living a story that was improbable, breathtaking and ultimately more satisfying than any story ever come across." She first told the story through an essay, "Four Good Legs Between Us", that was published in American Heritage magazine, and the feedback was positive, so she decided to proceed with a full-length book. The book received positive reviews for the storytelling and research. It was made into the Academy Award nominated film Seabiscuit .