The United States Marine Corps was originally the Continental Marines of the American Revolutionary War, formed by then-Captain Samuel Nicholas at Tun Tavern in Philadelphia, by a resolution of the Second Continental Congress on November 10, 1775. Captain Nicholas's order was to raise 2 battalions of Marines.
That date is regarded and celebrated as the date of the Corps' birthday. At the end of the American Revolution, both the Continental Navy and Continental Marines were disbanded in April 1783. The institution itself would not be resurrected until 1798. In that year, in preparation for the Quasi-War with France, Congress created the United States Marine Corps.
The first Marine Birthday Party wasn't celebrated until 1921 with the Marine Corps Order No. 47 by the 13th Commandant, Gen. John A. Lejeune.
"In every battle and skirmish since the birth of our Corps, Marines have acquitted themselves with the greatest distinction, winning new honors on each occasion until the term "Marine" has come to signify all that is highest in military efficiency and soldierly virtue."