By the time these stamps were issued (Type I earliest use late April, 1863, Type II earliest use early May, 1863), many Arkansas CSA postoffices had been occupied, and more were lost progressively through 1863. The Union took control of the Arkansas river in early 1863 by overrunning the fort at Arkansas Post 40 miles up the Arkansas River from its mouth into the Mississippi. Little Rock and Fort Smith were occupied in September 1863; Pine Bluff in October 1863.
Thus most Arkansas uses of the Engraved Archer & Daley stamps are from post offices in the Southwest portion of the state. The CSA state government moved to Washington after Little Rock was lost. The main CSA military position was built at Camden, a bluff city on the Ouachita river that could be resupplied by water from Louisiana.
Since these offices continued in operation to the end of the war, there are a number of covers with these two stamps extant, but the number is very small compared to uses elsewhere in the Confederacy.