The 1966 NFL season was the season after which was played Super Bowl I, though it was called the AFL-NFL World Championship Game. The league expanded to 15 teams with the addition of the Atlanta Falcons, thus an odd number of teams (making byes necessary). This was the last season that NFL teams were divided into just two groups called conferences, and only one round of playoffs was played, the NFL Championship game between the two conference champions. As the competitive war between the NFL and the American Football League reached its peak, the two leagues agreed to merge on June 8, 1966. Under the agreement: The two leagues would combine to form an expanded league with 24 teams, which would be increased to 26 teams by 1969, and to 28 teams by 1970 or soon thereafter. All existing teams would be retained, and none of them would be moved outside of their metropolitan areas. While maintaining separate schedules through 1969, the leagues agreed to play an annual AFL-NFL World Championship Game beginning in January 1967. The two leagues would officially merge in 1970 to form one league with two conferences. In the Western Conference, Green Bay's first loss was in Week Five, falling 21–20 in San Francisco to tie them with the Rams. The Rams' lost 35–7 to Minnesota the next week, and Green Bay stayed in front until Week Nine, when Minnesota beat them 20–17. Baltimore's 19–7 win over Atlanta briefly tied it with the Packers at 7–2–0 in Week Ten, but the Colts lost to Detroit the next week, 20–14. The Packers clinched the title in Week Thirteen. In the Eastern Conference, the St. Louis Cardinals took the early lead, winning their first five games. (The Dallas Cowboys were also unbeaten, but due to a bye in Week One, they had played one fewer game and thus were a half-game behind the Cardinals in the standings). The unbeaten teams met in Week Six, and both were still unbeaten after they played to a 10–10 tie. They would continue to keep pace with each other until they met again in week thirteen. The Cards took a 10–7 lead in the first quarter, but Dallas won 31–17 to take over the conference lead for good. The NFL Championship Game would have Dallas hosting Green Bay at the Cotton Bowl in Dallas. The Packers would jump out to a 14-0 lead early in the first quarter. But, the Cowboys would come right back and tie it up by the end of the first quarter. The game would remain a tight battle with the Packers prevailing for a final score of 34-27, and the right to play in the first Super Bowl against the Kansas City Chiefs. The first half of Super Bowl I was competitive, as the Chiefs out-gained the Packers
in total yards, 181–164, to come within 14–10 at halftime. But Green Bay safety Willie Wood's 50-yard interception return early in the third quarter sparked the Packers to score 21 unanswered points in the second half. Green Bay quarterback Bart Starr, who completed 16 of 23 passes for 250 yards and two touchdowns, with 1 interception, was named MVP.