These teams included the Buffalo All-Americans, Rochester Jeffersons and the Canton Bulldogs.
The primary reason the Olympics never joined the NFL during the early era was the state of Pennsylvania's blue laws which prevented football from being played on Sunday; as a result, no Pennsylvania team joined the NFL (which played most of its games on Sundays) until 1924, though because most teams were available to play on Saturdays, they were able to schedule exhibition games against NFL teams fairly easily.
However, almost a year later, on October 4, 1939, in McKeesport, while the Pirates won that game too, the semi-pro Olympics held them to a much closer score, 9-6.
However, the Olympics main rivals were the Pitcairn Quakers, another strong team from the Pittsburgh-area.
However, Pitcairn would win the second game due to a last minute field goal by Paul Rupp.