The reference to “the lost cause” was the secession of Southern America to form their country which came to naught.
What is the lost cause?
"The lost cause" is a term used primarily in the context of the American Civil War of 1861 to 1865 and the Confederate States of America. It refers to the ideology that seeks to justify the Confederacy's cause and its defeat.
The concept of a united America held some appeal in certain circles but it was not the central driving force behind the Confederacy. The Confederacy seceded primarily to preserve the institution of slavery and maintain the South's economic and political dominance.