Pope Pius IX never actually signed any kind of alliance or 'statement of support' with the Confederate States of America, but to those who understand the nuance of papal protocol, what he did do was quite astonishing. He acknowledged President Jefferson Davis as the "Honorable President of the Confederate States of America."
From this we can glean three things about Pope Pius IX..."
Pope Pius IX And The Confederacy
Via Hamp, SWR