Bring the Jubilee

The first alt history book? Perhaps. Proto-steampunk? Fo' sho'.

Ward Moore relates a tale of an alternative reality 1950s USA, where, 90 years ago, the Union lost the Civil War and now a divided North America struggles to get by. The industrialized North has decayed into a decrepit, poverty-stricken smogfest (hence the steampunk), while the South/CSA is put-putting along with slavery and agricultural stuff. Protagonist is a bookish history student who wins a scholarship to study at a fancy Dead Poets Society-esque college in rural Pennsylvania. There, he hits it off with a lady physicist, who... has invented a time travel machine! Hilarity ensues. Well, not really.