The year was a highly significant one for the Bengals, in both a football and a civic sense. On the football side, the Bengals moved into the NFL as part of the league's merger with the AFL. Paul Brown's quest in returning to pro football, following his ouster from Cleveland by Art Modell in 1962, had always been about re-joining the NFL. So when the Bengals began play in the AFL in 1968, it was key for Brown to know that the '70 NFL-AFL merger was already approved. There was much debate and controversy over exactly how the leagues would combine. The Bengals pushed strongly for a full merger, with the 26 clubs divided into two 13-team conferences. Other interests sought to keep the 16 NFL teams and 10 AFL teams in separate conferences of unequal size. But the full merger view prevailed, with the NFL's Baltimore Colts, Cleveland Browns and Pittsburgh Steelers agreeing to join the 10 AFL teams in the new American Football Conference (AFC). The remaining 13 NFL teams formed the National Conference. The Bengals were part of a four-team AFC Central Division, joined by Cleveland, Pittsburgh and the AFL Houston Oilers. Thus was born the twice annual "Battle of Ohio" between the Bengals and Browns.
The Bengals started horribly on the field, losing six of their first seven games, but they roared to life in winning their last seven and claimed the first AFC Central title at 8-6, by a game over Cleveland. The Bengals became, at that time, the youngest franchise (third year of existence) to reach the NFL playoffs. Baltimore squelched the Bengals 17-0 in the first round of the playoffs, but that Colts club would go on to win Super Bowl V, and Brown won the Associated Press NFL Coach of the Year award. On the civic side, 1970 was the debut season for Cincinnati's dual-sport downtown stadium, which would be the Bengals' home through 1999. It was announced on Jan. 9 that the facility was officially named "Cincinnati Riverfront Stadium," but in popular usage the name soon became just "Riverfront Stadium." Though seating capacity for football varied, due to whether the Reds' home baseball season was still on, the new stadium roughly doubled the capacity of Nippert Stadium. The Bengals first played at Riverfront on Aug. 8, defeating Washington in a preseason game. The first regular-season game was on Sept. 20, a 31-21 win over Oakland, with QB and future Bengals head coach Sam Wyche scoring the new facility's first regular-season football points, on a five-yard TD run in the first quarter. The club averaged 58,251 home attendance in the regular season. The baseball Reds had begun their tenure at Riverfront with a game vs. Atlanta on June 30.
The team selected QB Greg Cook of the University of Cincinnati with its first draft pick (fifth overall), and Cook was an immediate sensation. He led the second-year club to a 3-0 start, including victories over AFL powerhouses Oakland and Kansas City. "If (Cook) stays with it, I've got myself another Otto Graham," Paul Brown said. But Cook suffered a shoulder injury in Cincinnati's Game 3 win over Kansas City, and though he returned to play later in the season, winning the AFL passing title and league Offensive Rookie of the Year honors, he never fully recovered from the injury. The Chillicothe, Ohio native would play in only one more game after '69, and likely more than any other Bengals player, he has inspired thoughts of "what might have been." Cook's average-yards-per-pass-attempt in '69 was 9.41, still a team record through 2020 and the oldest surviving mark in the franchise record book. Although the team faltered after Cook's injury, finishing 4-9-1, Brown was named AFL Coach of the Year, and LB Bill Bergey, the team's second-round draft pick, was named AFL Defensive Rookie of the Year. Local support for the Bengals grew steadily, and on Oct. 7, the club announced that the remainder of the home season at Nippert Stadium was sold out. On Nov. 9, the Bengals played the franchise's first game on an artificial surface, tying Houston 31-31 at the Astrodome. The club experienced a tragedy on the morning of Sept. 15, day of the season opener, when LB Frank Buncom of Southern California, a 29-year-old about to enter his eighth NFL season, was found dead at the team hotel, due to a blood clot that had reached a lung.