You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
With a POD after 1849, your AH challenge--should you choose to accept it--is to have New England undertake armed rebellion against a Federal government that still commands the loyalty of the Southern states.
More states may join the New English ones, and the goals of the rebels need not necessarily be the same secessionist ones of OTL's ACW.
And before anybody points it out, yes, I understand that this is borderline ASB. But then, if it were otherwise, it wouldn't be much a challenge, would it?