Uh, I think you are mixing terms, so I'm confused. The Union is usually used in opposition to The Confederacy and their essential argument was about the expansion of slavery into the western territories. Segregation was a Democrat enacted set of laws usually known as Jim Crow in the South or just "the law" in the North. AFAIK, legal segregation wasn't as big a deal out West, but I'd not be shocked if that wasn't just my lack of historical knowledge. I think if you sat down and made an honest list of the similarities and differences between Jim Crow style discrimination and prohibitions against same-sex marriage you'd see how different they were. -XC PS - Other forms of discrimination practiced by states: drinking laws, voting laws, property ownership laws, divorce laws, parental rights laws, right to open a business, etc, etc. All discrimination, all not federalized.