A white curvilinear equilateral triangle having a 2 inch (5.08cm) chord, with one point down, pierced by an equilateral triangle 1 1/2 inches (3.81cm) from point to point having concave sides terminating 1/4 inch (.64cm) from each end, all on a dark blue curvilinear equilateral triangle having a 2 3/8 inch (6.08cm) chord.
The design was arbitrarily selected to represent the 3d Corps Area Service Command. White, being a mixture of all colors, was selected for the reason that Corps Area Service Commands may be composed of all arms and services. The geometric design represents the command's numerical designation.
The 3d Corps Area Service Command Headquarters was located in Baltimore, Maryland, and the Command was responsible for the states of Delaware, Maryland, Pennsylvania, Virginia and Washington. D.C. The shoulder sleeve insignia was originally approved on 17 Jul 1941. It was amended on 14 Oct 1941 to change the color of the background from olive drab to dark blue.