Interesting if you find bullsh--- fabrication and manipulation of statistics to be interesting.
The assertion was 1.4% of Americans owned slaves. Not 1.4% of Americans plus all their offspring owned slaves or 1.4% of Americans living in a certain region owned slaves, it was just 1.4% of Americans owned slaves. Yet this bullsh-- article essentially says 'let's just ignore that, reduce the denominator by more than half and then declare that 5% is more than 1.4%'. Brilliant!
Out of the 31m people in 1860, roughly 22m lived in the north and 9m in the south. By the author's stats, 4.9% of the southerners owned slaves, or roughly 440,000 people. 440k / 31m = 1.4% of Americans owned slaves. So the meme was in fact, true.