Book 22 in the Magic Tree House series (2000) A novel by Mary Pope Osborne If it's Wednesday, it must be Revolutionary War day. Jack and Annie, stars of the Magic Tree House series, are in for another adventure in their time- and space-traveling tree house. Mysterious magical librarian Morgan le Fay has set four new tasks for the siblings. Jack and Annie must find four special kinds of writing for Morgan's library in order to save Camelot, the ancient kingdom of King Arthur. In Civil War on Sunday, the pair traveled back to the 1860s to collect a list of rules (something to follow" from famous nurse Clara Barton. Now they discover they must visit another war era: the Revolutionary War. Jack and Annie set aside their apprehension and soon they're spinning back through time to Christmas Day, 1776, on the banks of the Delaware River in Pennsylvania, where they encounter none other than the man on the dollar bill himself, George Washington! The children accidentally-on-purpose end up embroiled in the famous commander-in-chief's mission, where they not only play a part in convincing Washington to carry on with his patriotic duty, but also find the second kind of writing for Morgan's library: "something to send.