Most folks can sing the refrain to "Take Me Out to the Ball Game," but fewer know the verses about a "baseball mad" girl named Katie Casey. In this sprightly story of the All-American Girls Professional Baseball League of the 1940s, Corey (You Forgot Your Skirt, Amelia Bloomer!) gives the fictional Katie a mitt and a powerful swing. Katie, with arms akimbo and a mischievous grin, "wasn't good at being a girl… at least not the kind of girl everyone thought she should be." The tomboy "prefer[s] sliding to sewing, batting to baking, and home runs to homecoming." She seems not to notice her home-ec teacher's anxiety or her parents' frowns at her unladylike interest. When professional men's baseball goes into decline during WWII, Katie travels to Chicago's Wrigley Field to try out for a nascent women's league; she's recruited to the Kenosha (Wis.) Comets. With a shrewd eye to '40s fashion and wavy hairdos, Gibbon (Poetry at Play: Outside the Lines) pictures the team playing in tan dresses, blue knee socks and caps, while Katie's once-disapproving parents smile in the stands. The sunny watercolor and colored-pencil illustrations situate one girl's experience within wider American history; on one spread, a casual portrait of FDR appears while, opposite, a draft notice lies in an abandoned ball field. Corey blends lively fiction and fact, and includes an enthusiastic afterword about her research into the AAGPBL (David A. Adler's Mama Played Baseball, illus. by Chris O'Leary, [reviewed Feb. 3] also explores the subject). Corey's latest title makes an impressive addition to her growing backlist of historical, feminist-themed picture books. Ages 5-8. (Apr.)