NFL Films states that this play is both the greatest play of all time and the most controversial play of all time.
Early in the 1972 season he Steelers won a regular season match up with the Raiders 34-28. The Steelers finished the season at 11-3 while Oakland posted a 10-3-1 record. Miami however had the best AFC record so oakland and Pittsburgh would battle it out to face the Dolphins in the AFC WildCard showdown.
It was a scoreless tie at the half. Oakland's longest play in the first two quarters was an 11 yard gain. Pittsburgh could have tried a 31 yard field goal but instead on 4 and 2 John Fuqua was stuffed by Jack Tatum and the Steelers turned over the ball on Downs. A foreshadow of a much more famous collision between the two later in the game. The Steelers kicked two second hald field goals and Oakland QB Ken Stabler scrambled for a 30 yard TD run. Woth 1:17 remaining the Pittsburgh held the ball trailing 7-6 on a 4-10 play.
Steelers quarterback Terry Bradshaw, under tremendous pressure from Raiders Tony Cline and Horace Jones, threw the ball to the Raiders' 35-yard line, toward halfback John Frenchy Fuqua. Raiders safety Jack Tatum collided with Fuqua just as the ball arrived. Tatum's hit knocked Fuqua to the ground and sent the ball sailing backward several yards, end over end.
Steelers fullback Franco Harris, after initially blocking on the play, had run downfield in case Bradshaw needed another eligible receiver. He scooped up the sailing ball just before it would have hit the ground. Harris ran past Raiders linebacker Gerald Irons, while linebacker Phil Villapiano, who had been covering Harris, was blocked by Steelers tight end John McMakin. Harris used a stiff arm to ward off Raiders defensive back Jimmy Warren, and went in for a touchdown. The touchdown gave the Steelers a 13–7 lead when Roy Gerela added the ensuing extra point.
Coach John Madden was livid as people flooded the field in panadmonium, and he had some legitimate gripes of contention.
Check it out for yourself on this great video of the play: https://www.youtube.com/watch?v=nT1NXb1Cwqg