What Katy Did is an 1872 children's book written by Sarah Chauncey Woolsey under her pen name Susan Coolidge. It follows the adventures of a twelve-year-old American girl, Katy Carr, and her family who live in the lakeside Ohio town of Burnet in the 1860s. Katy is a tall untidy tomboy, forever getting into scrapes but wishing to be beautiful and beloved. When a terrible accident makes her an invalid, her illness and four-year recovery gradually teach her to be as good and kind as she has always wanted. The fictional Carr family was modeled after her own, with Katy Carr inspired by Woolsey herself. The brothers and sisters were modeled on her four younger siblings.