[untenured]

That's one of the questions I have. How often do these occur? One reads all the time about cranks of one sort or another who want to overthrow the government, so I wonder if this is just another of hundreds of similar small-bore plots.

[mrsmith]

I guess it just depends on where you draw the line to consider it to be "serious", if it has no effect- which thankfully none seem to have had.
The Newburgh conspiracy was the most serious ever IMHO.

Other alleged 'coup attempts' I've heard of:
Were Washington and/or Hamilton planning a coup against President Adams with the Army Adams managed to never form?
Was Nixon planning a coup with the Marines, as some say Kissinger and Shlesinger arranged for the 82nd Airborne to counter?

An old thread on the Butler conspiracy with some good freeper input: Oliver Stone Sets Sights on Roosevelt (GOP conspiracy against FDR)