Name some experts from say 1860 who said that. Or even some from 1880 who said that.
It wouldn't have remained economically feasible after the industrial revolution.
The industrial revolution didn't hit most of the south, at least the prediminant crops of the agricultural south, until well into the 20th century.
You haven't heard of US Steel, in Birmingham, Al. or the textile mills in North Carolina, or the Cigarette factories? All those were before the 1900's if memory serves.