"My own observation of the real condition of the people of our Slave States, gave me ... an impression that the cotton monopoly in some way did them more harm than good; and although the written narration of what I saw was not intended to set this forth, upon reviewing it for the present publication, I find the impression has become a conviction."
He argued that slavery had made the slave states inefficient (a set amount of work took 4 times as long in Virginia as in the North) and backward both economically and socially.
Journeys and Explorations in the Cotton Kingdom was published during the first six months of the American Civil War at the suggestion of Olmsted's English publisher. To this he wrote a new introduction in which he stated explicitly his views on the effect of slavery on the economy and social conditions of the southern states.

Frederick Law Olmsted (1822-1903) was an American landscape architect, journalist, social critic, and public administrator. He is popularly considered to be the father of American landscape architecture.