Susan Coolidge, the pen name for Sarah Chauncey Woolsey (January 29, 1835 – April 9, 1905), was an American children's author best known for her classic coming-of-age series 'What Katy Did' chronicled in 'The Complete Katy Carr Series'. Born into a wealthy and influential family in Cleveland, Ohio, Woolsey worked as a nurse during the Civil War, an experience which deepened her compassionate insight into human nature and colored her later writing. She began her writing career as a poet before turning to children's literature. Her literary style is marked by its vivacious and sympathetic portrayal of young girlhood. 'The Complete Katy Carr Series' includes 'What Katy Did' (1872), 'What Katy Did at School' (1873), 'What Katy Did Next' (1886), 'Clover' (1888), and 'In the High Valley' (1890). These books follow the adventures and misadventures of Katy Carr as she grows from an impulsive, tomboyish child into a responsible and mature young woman. These narratives were praised for their depiction of realistic family dynamics and Coolidge's skill in capturing the intricacies of adolescent life. Coolidge's books, balancing morality and entertainment, were influential in the development of American children's literature, setting a precedent for writing that neither talks down to children nor neglects the complexities of growing up. Coolidge's enduring popularity rests on her blend of warmth, humor, and life lessons, securing her place in the pantheon of cherished children's authors.