Sarah Chauncey Woolsey (writing under the pseudonym Susan Coolidge) was a popular American author of kid's books best known for her series of books that follow a young teenage girl named Katy Carr. After the success of the first book, What Katy Did, Coolidge kept writing sequels, all about the semi-autobiographical protagonist, including What Katy Did Next, and naturally, Coolidge modeled Katy's siblings off her own family as well.