My gg-granduncle was the man who shot Wm. Quantrill, John Langford. I obtained a letter he wrote about it from the Filson Historical Society. Southern Mississippi University has a rather large file about Quantrill
You may be able to find out more there.
Why, yes, the Free States *were* afraid of the South's excess political power. The slaveocrats had been using the extra clout of the 3/5ths rule to impose their will on the Free States for decades. See my earlier reference to the Fugitive Slave Law, etc. But shifting demographics (mostly due to a large immigrant influx into the Free States) was causing a power shift that the slaveocracy could not stomach.
So yes, money and greed, but the capital was tied up in human form. To separate the capital (money) from the form (slavery) is splitting hairs that doesn't really wash.
To the mod: So if someone promulgates lies, we're just supposed to sit here and say, 'I can't refute that, it's the wrong thread'?