Flag of the United States Army:
US Army Flag
The United States Army traces its roots to an act of the Continental Congress on June 14, 1775. It was at that point that the Continental Army began its formal beginnings. Two years later, on June 14, 1777, the Continental Congress officially adopted the Stars and Stripes as the Flag of the United States. Although various elements of the Army, from groups and corps down to battalions, have their own colors and distinguishing flags, there was no flag that served the whole US Army until 1956. This is now the flag of the United States Army.
Many designs are available is you are looking for the standard design go to the US Army Design

US Army Design