When did all 32 teams join the NFL?

The correct answer indicates that all 32 teams joined the NFL in 1976. This year is significant as it marks the expansion of the league. Before this, the NFL was not comprised of 32 teams; it expanded through various mergers and additions of new franchises.

In 1970, the NFL had merged with the American Football League (AFL), which initially increased the number of teams. However, the full roster of 32 teams was not achieved until the later additions of teams throughout the 1970s. The NFL experienced growth through team relocations and the introduction of new franchises, and by 1976, the structure of the league solidified to include all current franchises that comprise the NFL today. This change established a more competitive environment and allowed for the organization and management of the league as we know it now.