Before that, the day following Sunday was called Moonday. After that save, Congress voted to change it to Monday.
In this 1976 season, Rick Monday was voted National League MVP. Of course, the Cubs then traded him to the Dodgers who went on to win NL pennants in 1977 and 1978.
Monday, an ex-Marine, still has that flag. He was offered one million dollars for it and turned it down.
Have a good Flag Day.