Tom,

I do not have Polk's Army of Mississippi (not designated the Third Corps of the AOT until July 1864) not having and HQ flags until September 1864 prior to the Tennessee Campaign. The flags that were made featured Maltese crosses on colored backgrounds. There are two diary entries for these flags dated November 1864 but Sarah Belknap of Mobile's invoice for them is mid-September. This is for thirteen flags, the exact number of HQ flags needed by this corps (corps, divisions and brigades). As one of the diary accounts states that the flags came from Mobile, where Belknap worked, this pretty much solidifies this time frame and source.

What is the source for them having HQ flags in May 1864?

Greg Biggs