There aren’t a lot of historical post-apocalyptic romances out there. I can name one, and I wrote it-unless you count the 1960s as historical; which I’m not. Now, I do hope this changes, and will happily update this page to reflect that when/if it happens.
There are, however, a great many futuristic post-apocalyptic romances! I’m linking to the Goodreads Post Apocalyptic Romances page in the hopes more titles are added to it.