On January 15th, 1967 the AFL and NFL went head to head for the first time in a national championship.
SOURCES
The First Super Bowl Half-Time Show Rocket Men
NFL Network Ad for Super Bowl I: The Lost Game
CNN: The Lost Footage of Super Bowl I
NFL Network: Super Bowl I: The Mystery of the Lost Tapes
NFL Network: Super Bowl I: The First AFL-NFL Championship Game | Chiefs vs. Packers
The New York Times: Out of a Rare Super Bowl I Recording, a Clash With the N.F.L. Unspools