I've been reading State by State: A Panoramic Portrait of America. My home state's contribution, by Daphne Beal, mentions the author learning "eighth-grade paleontology, dating from some 500 million years ago, when Wisconsin was still under a shallow inland sea."
I would like to point out that Wisconsin was under a shallow inland sea for several days this summer, as some crazy monsoons hit us.
Other thoughts: Illinois by Dave Eggers is riotously good. California by William T Vollmann is depressing and a trifle sanctimonious. Massachusetts by John Hodgman is funny, of course, but punctures forever the illusion of the 'most liberal state in the country.' Speaking of the most liberal state in the country, Washington by Carrie Brownstein is also a very good read.