Nobody, because the NFL wasn't formed until 1920.
1919 and joined the NFL in 1921.
The Packers were founded in 1919 and joined the NFL in 1921. The Vikings were founded and joined the NFL in 1961.
In 1919 and 1920 they were a semi pro team and joined the pros in 1921.
The Chicago Bears, who were founded in 1919 and joined the NFL in 1920. The only remaining team from the NFL's first season in 1920 are the Cardinals (the oldest team; founded in 1898)
they joined the NFL in 1925
The Green Bay Packers were founded in 1919 and joined the NFL in 1921. The only team that's older is the Arizona Cardinals, which were founded in Chicago in 1898. The Chicago Bears are the third oldest, beginning in 1920.
The Packers joined the NFL for the 1921 season.
Both the Seattle Seahawks and Tampa Bay Buccaneers joined the NFL in 1976. Seattle joined the AFC and Tampa Bay joined the NFC. Due to divisional realignment Seattle is now an NFC team.
The Vikings joined the NFL as an expansion team in 1961.
The New Orleans Saints joined the NFL in 1967.
The Cowboys joined the NFL as an expansion team in 1960.
The Cowboys joined the NFL as an expansion team in 1960.