Thanks for note, I’ve added it to my hospital flag files.
The US Army regulations (1854) called for a red flags for hospitals at the beginning of the war, dating back to the reorganization of Amy soon after the War with Mexico. Red flags were used, starting with the French Army in the 1700’s and later on in England. General Beauregard issued orders that red flags were to be used to mark the locations of Hospitals, of the Confederate Army of the Potomac. It appears that General Beauregard copied the U.S Army regulations of 1854. Several late war captured red Confederate Hospital flags survive.
The yellow quarantine flag was adopted, per Act of Congress, in 1798 to mark the locations of the “Marine Hospital Service” (Government run) Hospitals. The yellow quarantine flag was first used by the City of Philadelphia in 1699 to mark the locations of sick seamen under the maritime quarantine laws. In 1860 there was nineteen “Marine Hospital Service” hospitals along the eastern cost and several other along the Gulf of Mexico cost. At the beginning of the war those hospitals were taken over for military use in the north and south. The U.S. Army did not adopt the yellow hospital flag until 1862, General Orders 102, Army of the Potomac. The Department of the Rappahannock in 1863, General orders 53. Department of the Cumberland as with the Army of Ohio later in 1863 adopted the yellow flag for hospitals. The Army of the West replaced the red flag for hospitals with an U.S. National flag in early 64. Later in 64 they conformed to an Act of Congress of the yellow flag with the green H.
The U.S. Hospital Department, The U.S. Medical Service and the Ambulance Department were separate departments and had deferent regulation regarding flags and the deferent departments had their own hospitals. In most cases the word hospital refers to the larger general hospitals in larger cities & towns, field hospitals located near the battle field and aid stations or ambulance depots located at the rear of the army on the field of battle.
The yellow flag shows up very early for Confederate hospitals regardless of the orders from General Beauregard. Many of those hospitals were run by civilian doctors so Army regs didn’t apply, I guess. As with the U.S. Army, the Confederate Medical Service and the Ambulance Department were deferent departments. The Ambulance Department pretty much followed orders on the use of red flags for their field hospitals and depots, while the Medical Department used yellow flags, they had more civilian doctors then the Ambulance Department. It is documented that in fairly safe areas, Hospitals were usually just marked by a national flag, both north and south. There is supported data that the Confederate Army used red and white flags to ID their Ambulance trains. There is also data that the U.S. Army used small Corps flags bordered in green on their Ambulance trains. By trains, I mean both the coal powered ones and the horse powered ones.
On the regimental level, both north & south, both color flags were used to mark aid stations. I have more documentation on the use of yellow flags at this level of medical care for the troops.