Allright, some highlights I would recommend based on my travels throughout the US:
If you're heading east through the midwest to Ohio, you're probably traveling close to Chicago, if not right through it. I recommend you stop by the Windy City and try the next 3 things at least once: the italian beef, a Chicago style hot dog, and a Chicago style pizza. This is to prepare you in case you go to New York and try their (inferior) pizza. You'll at least know what good stuff tastes like. : ) Beyond that, the lakefront in Chicago is beautiful, especially if you visit near summer. You can visit Navy Pier, or walk Lake Shore Drive, or just stroll through Grant Park. Wonderful area. While you're in the area, we can play some Dip as well : p
Outside of Chicago, on the way east, there's Gary, Indiana. If you happen to be a Michael Jackson fan, you can swing through and see the (tiny) house he grew up in. If not, you can smell the wonderful smell of the steel mills (not as bad as it used to be though).
I'm afraid I don't know overly much about the rest of Indiana/Ohio, but once you pass Ohio (if you so choose), I-80 will take you near Pittsburgh (mentioned previously I believe). Further east in Pennsylvania, you can visit Philadephia, our nation's first Capital, and the location where the Continental Congress meetings were held as well as where the Declaration of Independence was signed. Between the 2 cities is Gettysburg, which as I previously mentioned, I highly recommend going to if you're looking for anything related to historical battles. It was the turning point of the American Civil War, and one of the most important battles in US history. In addition, the battlefield is superbly maintained and looks very close to what it would have looked like in 1863. They have guided "battle-walks", or you can explore on your own. Highlight areas include Seminary Ridge (Day 1 fighting, mostly because my ancestor fought there on that day, so go see it!), Devil's Den, The Peace Orchard, and Little Round Top (Day 2 fighting, Little Round Top being probably the best chance the Confederates had at turning the Union line and coming away with the win at Gettysburg), and Pickett's Charge (Day 3 fighting, considered the High Water Mark of the Confederacy where the plan was to smash the Union Center and claim victory with a 1 mile march over open ground). If you can't tell, I like Gettyburg a lot. : )
Past Pennsylvania, we have nearby Washington D. C. to the south which I highly recommend going to. As a city designed purely as a Federal City, it's pretty cool to see the epicenter of American power in D. C. Not only that, but there's some pretty cool monuments to see as well.
To the north, there's obviously New York (doesn't need too much explaining), and further on, Boston. Personally, if you're into history, I recommend Boston. While there, you can see Lexington and Concord, the first battles of the American Revolution, as well as historic Boston.
At this point, I'm going to bow out, as I think I've written more than I intended. I'm sure I'll pop back in with more though. God bless the USA!