INSIGNIA OF RANK
The size of the Army does not permit Army officers in charge of a large group to know all in their command by their name, nor is it possible to know all the duties of the various individuals of an organization if placed in a command, but by means of insignia of grade anyone trained in military organizations and tactics may quickly have a title by which he or she may address an individual and based on the responsibilities commensurate with each grade, they may issue orders intelligently.
General Washington was chosen by the Continental Congress and was informed on June 16, 1775 that he was to be general and commander-in-chief to take supreme command of the forces raised in defense of American liberty. Just thirty days later, on July 14, 1775, a General Order was issued which read: "To prevent mistakes, the General Officers and their aides-de-camp will be distinguished in the following manner: The Commander-in-Chief by a light blue ribband, worn across his breast, between his coat and waistcoat; the major and brigadier generals by a pink ribband worn in a like manner; the Aides-de-Camp by a green ribband."
On July 23, 1775, General Washington states "As the Continental Army has unfortunately no uniforms, and consequently many inconveniences must arise from not being able to distinguish the commissioned officers from the privates, it is desired that some badge of distinction be immediately provided; for instance, that the field officers may have red or pink colored cockades in their hats, the captains yellow or buff, and the subalterns green."
Our present system of officers grade insignia began on 18 June 1780 when it was prescribed that Major Generals would wear two stars and Brigadier Generals one star on each epaulette. In 1832, the Colonels eagle was initiated and in 1836, leaves were adopted for Lieutenant Colonels and Majors, while Captains received two bars and one bar was prescribed for First Lieutenant. Second Lieutenants did not receive the gold bar until December 1917.
Warrant Officers were provided with an insignia of identification on May 12, 1921, which also served as their insignia of grade. In 1942, Warrant Officers were graded and there were created a Chief Warrant Officer and a Warrant Officer (Junior Grade), and separate insignia of grade (gold and brown enamel bars) were approved June 14, 1942. A grade of Flight Officer came into being in 1942, and the insignia was prescribed to be identical to Warrant Officer (Junior Grade) except the enamel was blue instead of brown.
Other than the dates of authorization, nothing has been located as to why the leaf and bar was selected for officers insignia. Military routinely incorporate the design representing their country in their insignia and the eagle with shield, arrows and olive leaves was taken from the Coat of Arms of the United States.
Information Courtesy of U.S. Army