https://www.govinfo.gov/content/pkg/STATUTE-90/pdf/STATUTE-90-Pg2078.pdf
“Whereas it is considered fitting and proper that no officer of the United States Army should outrank Lieutenant General George Washington on the Army list: Now, therefore, be it Resolved by the Senate and House of Representatives of the United States of America in Congress assembled, That . . . The President is authorized and requested to appoint George Washington posthumously to the grade of General of the Armies of the United States, such appointment to take effect on July 4, 1976.”
‘....Technically, the law decreeing that no military official could outrank Washington didn’t specifically grant a six-star general designation. But some argue Washington’s ascension to such a rank means exactly that, and newspapers even reported it as such back in 1976.’
Give the guy 6.