Is it true that most slaveholders owned more than twenty slaves?
No, it is not.
In the South there were 7,8 millions of whites and 200,000 free
blacks, of which:
6,100,000 owned no slaves,
1,400,000 owned from 1 up to 10 slaves,
300,000 owned from 10 up to 20 slaves and
200,000 owned more than 20 slaves.