I once read a book where the Confederate States of America, on the verge of total defeat in the spring of 1865, makes a dramatic come back, and conquers the entire United States of America. In the late 19th century, they end slavery, and establish a "separate but equal" system that is literally true. One house of the Confederate congress is 100% white, the other house is 100% African-American. Whites and blacks have full equality, but marriage between the races is strictly forbidden and seen as a crime at least as bad as murder. The southern states remain an idealized, agrarian paradise, while all polluting industry is located in the ex-United States, the "industrial zone".
By the late 20th century, the CSA is by far the wealthiest country in the world, having benefited from much immigration from Europe as an oppressive and militarist Germany gradually conquered almost the whole continent.
I am not making this book up, but I can't remember the exact title. It came out maybe 10 or 11 years ago. I thought it was actually an interesting idea for a very different kind of American society, but as far as plausibility goes, it gives Harrison's trilogy strong competition.
