In almost every history lecture on the subject I've heard that the Lost Cause began in the 1870s and 1880s and it was solidified in the 1900s by the United Daughters of the Confederacy.
I came across Marx' Oct. 20th 1861 letter to Engels where he said that he was tired of seeing the British press classify the American Civil War ("The Economist, The Examiner, The Saturday Review and tutti quanti expounded the theme further.") as a "tariff war" and he seems to clearly address most of the popular Lost Cause talking points.
This left me confused. Do you start with Jubal A. Early's articles to the Southern Historical Society, the contemporary British press, or elsewhere? If it was the British press, why would that argument have been popular for the at the time?
I answered a similar question a couple of years ago that addressed the roots of the "State's rights" causal argument in Civil War history, which I think addresses this Lost Cause origin question to a certain extent. I hope it helps a bit!