[iowamark]

Pershing was “General of the Armies,” the only one to hold this rank. He never wore more than 4 stars in public.

[jpsb]

From wiki

General of the Armies of the United States, or more commonly referred to as General of the Armies, is the highest possible grade in the United States Army.

Only one man has been appointed General of the Armies in his lifetime, and one other posthumously:

John J. Pershing in 1919 to honor his service in World War I.
George Washington (posthumously) in 1976, as part of the American bicentennial celebrations, to commemorate his leadership and involvement in the founding of the United States, was appointed "to the grade of General of the Armies of the United States