I teach John Brown's raid on Harper's Ferry as an act of treason against the U.S. government. I draw a throughline between Jackson's 1832 doctrine, the mass resistance in northern states to the fugitive slave act of 1850, John Brown's raid, and the firing on Ft. Sumter. I'm not a lawyer, but I think that for historical purposes you can lump all these things together as acts of treason / armed resistance against the U.S. government.

I ask my students to consider these various lawless acts and examine the question of how law and morality intersected, particularly in the case of John Brown. Was he a freedom fighter or a domestic terrorist? Was what he did right or wrong? I ask my students to think about whether at any of these stages people could have chosen another route, or could have seen another route, to achieve what they believed was just, and whether we in retrospect can see a possible course of action that people at the time didn't see open to them. If the civil war was not inevitable (and nothing in history was, just as nothing today is), then it's important to understand the multitude of choices that made it seem so to people at the time.

That's how I teach this period. But, as I said in the post, I would move up the "official start" of treasonous rebellion up to Nov. 7, not Dec. 20 and certainly not as late as April of 1861.