Research Exercise: What Percentage of Southerners Supported the Confederacy?

Here’s a research exercise that should engage some people (including a certain mathematician who reads this blog frequently):

What percentage of southerners supported the Confederacy?

For purposes of this exercise, we hold to the following definitions:

1.  “The South” is defined as the fifteen slave states of the 1860 census. We are not including New Jersey or points west (that would make this too easy to define the Confederacy as a minority movement). Nor will we count the Indian Territory later known as Oklahoma.

2.  All people counted in the 1860 census–free and enslaved–regardless of race or color, are defined as southerners. Recall that the three major categories are whites, free blacks, and enslaved people.

Left to you is to offer an estimation (complete with justification) of the number of southern whites who stayed loyal to the Union.

Show your work so that we may follow your reasoning. Let’s allow until next Monday as the deadline for solutions.