George Washington

This 1790 portrait of George Washington at Princeton by Charles Peale Polk hangs in the Smithsonian Museum of American History in Washington, DC.

"George Washington made two memorable visits to Princeton. In 1777, only ten days after crossing the Delaware on Christmas night and defeating the British at Trenton, he drove the British from Nassau Hall and sent them retreating from Princeton. The second visit was in 1783 during the closing days of the war when he appeared at the Continental Congress which was meeting in Nassau Hall." -- The Price of Freedom

 

"Charles Peale Polk was born in Annapolis, Maryland, on 17 March 1767. Polk was the son of Elizabeth Digby Peale, the younger sister of the celebrated artist and naturalist Charles Willson Peale and Robert Polk. When he was orphaned at the age of ten, Polk went to live in Philadelphia with his uncle’s family. He received the same benefits of education and artistic training as his cousins and grew to rely heavily on the style of Charles Willson Peale." -- Museum of American History

The Smithsonian institution points out the epaulets in Polk's painting and displays a pair of Washington's actual epaulets nearby.

Symbols of Rank

George Washington took special care to outfit himself in a fashion suitable to a commanding general, believing that “the person commanded yields but reluctant obedience to those he conceives are undeservedly made his superiors.” He wore epaulets on the shoulders of his uniform, and sometimes a blue ribbon to distinguish himself. -- NMAH

Specific History

These epaulettes were worn by George Washington and can be seen in life portraits painted by celebrated American artist Charles Wilson Peale between 1779 and 1780.-- NMAH

General History

The British Army, which served as the model for the Continental army, adopted epaulettes as officers' rank insignia in 1768. Continental army regulations for the use of epaulettes were first published in the General Orders dated June 18, 1780. According to these orders, major generals were to wear an epaulette on each shoulder with two stars on each epaulette. A brigadier general wore an epaulette on each shoulder with one star on each epaulette. -- NMAH

In Polk's painting Washington has three stars on his epaulets; He was the first Lieutenant General in the US Army.

In the outpouring of patriotic fervor  that accompanied the bicentennial year 1976, it was proposed  that since the ranks of the U.S. general officers had inflated to include 4 and 5 star generals, Washington should be posthumously promoted so that no one would out-rank him. Congress passed the legislation in 1976 and it was signed by President Ford. In 1978 this order was given promoting Washington to General of the Armies effective date July 4, 1976.

Many interpret this as effectively making George Washington a 6-Star General.
See this video from Mount Vernon:

Another page at Mt. Vernon, "Charles Peale Polk and His Famous Uncle" contrasts this painting with Charles Willson Peale's portrait of Washington at Princeton.