The single digit percent number is counting people in States where slavery was illegal as well, which is why it's so low.
According to census data, about 1/3 of homes in the south had slaves, with most households having less than 20.
As
@AWP said, you can make the case the war was really about economics, which is accurate. Then we gotta ask the followup question though.
What economic policy were they upset about? The economics of chattel slavery.
Most southerns didnt own slaves, but that's due to cost, not desire.
This
Reddit thread on ask historians (great sub btw) goes a bit more in depth, including the economic questions.
This is a misunderstanding of history. Sherman issued a field order saying some ~20,000 slaves in the Southeast be granted
40 acres and a mule. It was overruled by Andrew Jackson later that year.
Yup. We have records of the number of slaves, but thats only because they counted for population. Otherwise, they were basically considered farm animals, and nobody keeps geneaology of their chickens.