What Katy Did is a children's book written by Susan Coolidge, the pen name of Sarah Chauncey Woolsey. It follows the adventures of Katy Carr and her family, growing up in America 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 recovery gradually teach her to be as good and kind as she has always wanted.