nobody knows
The NFL and AFL merged in 1970.
Answer1970, but they entered the AFL in 1959.
The Chiefs became an NFL team in 1967 when the AFL merged with the NFL to become one league. They were one of the original AFL teams. They were still in the AFL until 1970, they won the Super bowl IV in 1970 as the last AFL team, the following year they joined the NFL as part of the AFC The Chiefs were originally named The Dallas Texans and was founded by Lamar Hunt as a member of the American Football League(AFL). The Chiefs relocated to Kansas City in 1963 and took the name that they have now. They then joined the NFL during the NFL-AFL merging in the year 1960.
1970 - they had been in the AFL previously.
The Dolphins began as an AFL team in 1966 and entered the NFL in the 1970 merger of the two leagues.
The two leagues merged in 1970.
1970. They had been in the AFL in the 1960-69 period.
NFL by far!
The NFL began in 1920 and the AFL began in 1960. The two leagues merged in 1970.
150 years for afl
Well im not sure how, but NFL stands for National Football League. There used to be the AFL (American Football League) but the NFL and AFL merged.