The Kentucky Derby Museum site has a kid's section with a great reading list, and you can download a free Abraham Lincoln lapbook here.
I lucked out and found this book in brand new condition at the thrift store, but it is also available here. If you want an all-in-one place to keep up with state studies, this is very thorough and user-friendly, with maps, timelines, journal pages, and more. The only drawback to this format over a looseleaf notebook is that you can't cut and paste too many items in this one because of the binding, but you could take it to a print shop and have the binding sliced off and holes punched.
You can request tourism brochures which most states will mail you for free by doing a search for the department of tourism or chamber of commerce for the state you are studying. These make great cut-and-paste additions to the notebooking pages. My kids enjoy drawing the state flower, bird, and flag themselves most of the time, but the cut-outs are a nice time-saver when the artistic muse is on vacation.