After my visit to Cassville, I started to wonder: if the “Federals” took the town in May of 1864, why did they wait until November to fire it? The Etowah Valley Historical Society provides an answer:

This change in name [from Cassville to Manassas] is said to have been one of the reasons for the utter destruction of Cassville in 1864. Most likely, activities of Confederate scouts in and around Cassville stirred up anger among the Federal occupiers. Attacks on the nearby railroad and Federal supply trains steadily eroded Cassville’s peaceful existence. Many of the Confederates also found refuge among its citizens, a fact well known to the Federals. The murder at Cassville of ten soldiers, who were with a Federal wagon train, finally brought the anger of the Union Army into focus. On the night of October 11, the bodies of nine of them were left on the grounds of the Female College. In retaliation, the Male and Female Colleges and homes of President Rambaught and Judge Nathan Land were burned the following night. On the 5th of November, the 5th Ohio Regiment with approximately 300 cavalrymen set fire to the remainder of Cassville, leaving the churches and a few homes that were used as hospitals.

Here is one of the churches that escaped, Cassville UMC:

On November 15 Sherman began his March to the Sea, and the 5th Ohio Cavalry went with him.

By the way, Cassville would probably have been rebuilt, save for the fact that the railroad now passed it by. This more than anything explains the migration of the county seat to Cartersville.