Susan Coolidge was born in 1835 in Cleveland, Ohio, but grew up in Connecticut. During the American Civil War, Coolidge worked as a nurse. Susan Coolidge loved writing stories even when she was a child, and What Katy Did is based Susan and her brothers and sisters when they were young. Susan, like Katy, was a high-spirited, imaginative little girl, who often got into trouble. Her realistic portrait of childhood set her apart from other writers of her time; instead of teaching morals, she was interested in her characters, their imperfections and the dynamics of a family. The 'What Katy Did' trilogy was a huge success.