The position of aide-de-camp was created in the Continental Army in May 1778 when the Continental Congress passed resolutions station that two “Aids-de-camp allowed to each major general.” From that time onward, aides to the Commander-in-Chief and General Officers of all grades have been worn by special appurtenances to identify them as assistants to senior commanders. Since 1902, aides have worn collar devices consisting of an eagle clutching a red-and-white striped shield carrying the number of stars representing the rank of the General Officer they serve.
The three-star rank dates back to the Revolutionary War, but only one officer—
George Washington—was appointed to the grade. Despite the three stars he wore on his epaulets, however, Washington was not called Lieutenant General at that time. Instead, he was designated the “General and Commander in Chief.” Washington became the first General Officer to hold the rank titled Lieutenant General in 1798, when then-president John Adams appointed him Commander in Chief of the United States Army during the Quasi-War with France (he did not serve on active duty while at that rank, however). The rank was abolished in 1799 and was not re-established until Winfield Scott received a brevet promotion to Lieutenant General in 1855.
Today, the total number of active-duty Lieutenant Generals is limited by statute, which states that the maximum number of General Officers above the grade of Major General (two-star) at any single time is 46, which means the actual maximum number is determined by subtracting the number of four-star Generals from that limit of 46.
While both Generals and Lieutenant Generals are temporary positions normally filled during times of war, officers appointed to those ranks almost always retire at the higher grade rather than reverting back to Major General.