Former Cleveland Browns head coach Paul Brown began planning for the creation of the Bengals franchise in 1965, and Cincinnati's city council approved the construction of Riverfront stadium in 1966.[1] On May 23, 1967, Cincinnati was granted a franchise in the American Football League.[2] The franchise was sold to a Cincinnati-based ownership group led by Brown, who had an ownership share of 10%. The other investors included Austin E. Knowlton who was the majority shareholder with 30%, John Sawyer with 20%, The Cincinnati Enquirer with 11% and seven others who had a combined ownership share of 29%.[3]

As a founder and head coach of the Cleveland Browns from 1946 to 1962, Brown led his team to a .759 winning percentage and seven championships, which includes four championships earned while a member of the All-America Football Conference. The Browns were champions of that league in each of the four years it existed. When the AAFC folded after the 1949 season, the Browns, as well as the San Francisco 49ers and the first incarnation of the Baltimore Colts, were absorbed into the National Football League.

Brown became a recognized innovator for his approach to training, game planning, and the passing game. However, he was only a minority owner of the Browns and lacked the resources to buy out the rest of the ownership group. In 1961, businessman Art Modell assumed control of the team and on January 9, 1963, Modell controversially fired Brown. Many believe that Modell had tired of complaints of Brown's autocratic style; others claim it was Brown's decision to trade for Syracuse University's Heisman Trophy-winning running back Ernie Davis, who was drafted by the Washington Redskins, without Modell's knowledge. However, Davis was diagnosed with leukemia shortly afterward. Brown didn't want to play Davis; Modell insisted he could play. The relationship between Paul Brown and Art Modell, which was never warm to begin with, deteriorated further. Davis died on May 18, 1963.

By 1966, Paul Brown wanted to become involved in professional football again. James A. Rhodes, then the governor of Ohio, convinced Brown that Ohio needed a second team. Cincinnati was deemed a logical choice. Brown initially sought a franchise in the National Football League but had been rebuffed, in no small part because Cincinnati did not have an adequate facility. The city's largest football venue then in place, the University of Cincinnati's Nippert Stadium, seated only 28,000 people, nowhere near the minimum 50,000 capacity the league required for prospective expansion teams. The NFL deemed it unsuitable even for temporary use.

Brown named the team the Bengals in honor of an earlier Bengals team that played from 1937 to 1941, most notably in the second and third American Football Leagues. While playing as an independent team in 1938, the original Bengals defeated the Chicago Bears and tied the Chicago Cardinals in exhibition games.[4] Brown knew the original Bengals had made a good account of themselves on the field, and named his team the Bengals in order "to give it a link with past professional football in Cincinnati." [1] Possibly as an insult to Art Modell, Paul Brown chose the exact shade of orange used by his former team. He added black as the secondary color. Brown chose a very simple logo: the word "BENGALS" in black lettering.

A turning point came in 1966 when the American Football League agreed to a merger with its older and more established rival. Merger negotiations had been complicated by several factors, one being that members of the United States Congress were seeking guarantees that any merger would include all existing AFL teams. Under pressure from Congress, NFL commissioner Pete Rozelle had promised that professional football would be maintained in each of the twenty-three markets where it then existed. There were a total of 24 franchises in the two leagues at the time (fifteen in the NFL and nine in the AFL), but the powerful congressional delegation of Louisiana led by Senator Russell Long and Congressman Hale Boggs had further insisted on an NFL franchise in New Orleans in return for their support. As a result, the New Orleans Saints became the NFL's sixteenth franchise in 1967.

Having just stocked the Saints' roster, the NFL's owners did not want to risk having the talent pool of their own league becoming further diluted by way of another expansion draft. They also realized that an odd number of teams would unbalance the schedule. The NFL owners quickly agreed that the AFL should add another team. From the AFL's perspective, adding another team was highly desirable because the guarantee of an eventual place in the NFL meant the league could charge a steep expansion fee of $10 million – 400 times the $25,000 the original eight owners paid when they founded the league in 1960. The cash from the transaction provided the American Football League with the funds needed to pay the indemnities required to be paid by the AFL to the NFL, as stipulated by the merger agreement.

Prior to the merger being announced, Paul Brown had not seriously considered joining the American Football League, and was not a supporter of what he openly regarded to be an inferior competition, once famously stating that "I didn't pay ten million dollars to be in the AFL."[5] However, with the announcement of the merger, Brown realized that the AFL expansion franchise would likely be his only realistic path back into the NFL in the short term. Brown ultimately acquiesced to joining the AFL when after learning that the team was guaranteed to become an NFL franchise after the merger was completed in 1970, provided a larger stadium was completed by then. An additional consideration was that the AFL was willing to allow Cincinnati to play at Nippert Stadium for the team's two pre-merger seasons, buying them time to find another stadium.

Ultimately, the stadium issue was settled in no small part because the Cincinnati Reds of Major League Baseball were also in need of a facility to replace the antiquated Crosley Field, which they had used since 1912. Parking nightmares had plagued the park as far back as the 1950s, the little park lacked modern amenities, and New York City, which after 1957 had lost both their National League teams, the Dodgers and the Giants to Los Angeles and San Francisco, respectively, was actively courting Powel Crosley. However, Crosley was adamant that the Reds remain in Cincinnati and tolerated the mounting problems with the Crosley Field location, which were increased with the Millcreek Expressway (I-75) project that ran alongside the park.

With assistance from Ohio governor James A. Rhodes, Hamilton County and the Cincinnati city council agreed to build a single multi-purpose facility on the dilapidated riverfront section of the city. The new facility had to be ready by the opening of the 1970 NFL season and was officially named Riverfront Stadium, which was its working title.

With the completion of the merger in 1970, the Cleveland Browns were moved to the AFL-based American Football Conference. Unexpected victories for AFL teams in Super Bowls III and IV had persuaded NFL owners, starting with Art Modell, to re-consider the question of divisional alignments and ultimately led to the Browns and Bengals both being placed in the AFC Central. An instant rivalry was born, fueled initially by Paul Brown's rivalry with Modell. The Bengals played their inaugural season in 1968.