Interesting book from a historian of the Civil War. Heather Cox Richardson
https://www.amazon.com/How-South-Won...dp/B0862GM7HF/
In addition to her book, she posts almost daily and frequently draws parallels from the mid 1800's to today.
As I recall from the book, some of Lincoln's urgency was the expansion west and the fight was to ensure new western states didn't adopt slavery. It was a federal vs state's rights issue, drawing some of the parallels with today. Also interesting in her book is the reversal of party positions.
As a purple state, any discussion of NH succeeding is nonsense, as the title of this note states, but it makes for good winter jawboning.