Our family is going to Philadelphia this weekend:  Axel (my husband) is giving a talk at the University of Pennsylvania on Saturday, and the kids and I are tagging along.  Not to the conference, thankfully (sorry, Axel):  we'll be visiting the historic area.  Leo, my second-grader, likes colonial and revolutionary American history, so he's particularly excited about the trip.  He and I have been reading about the people who lived in Philadelphia (mostly about Benjamin Franklin) and the events that took place there during that period (the signing of the Declaration of Independence).  What he really wants to see, of course, is the Liberty Bell; that, and buy a replica of it (n.b, there are a lot of children's books about saving the Liberty Bell).  Favorite Philadelphia books will be in this space on Monday.