By shortening the land distance for those who needed to cross the bay, the Rio-Niterói Bridge also paved the way for the merger of the states of Guanabara and Rio de Janeiro, which which took place on March 15, 1975.

Until then, the two territories belonged to separate federal units. While the city of Niterói was the capital of the state of Rio de Janeiro, the state of Guanabara consisted solely of the municipality of Rio de Janeiro—an unusual “city-state” status that, until 1960, had housed the federal capital.

As early as 1968, when the construction of the Rio-Niterói Bridge began, public opinion polls published in the newspaper Correio da Manhã showed that both residents of the state of Rio de Janeiro and the city of Rio de Janeiro were in favor of merging the two states. There was also an almost unanimous belief that the bridge would help accelerate this process.

Enacted by President Ernesto Geisel on July 12, 1974, the law that determined the union of the two states gave rise to a new federative unit: Rio de Janeiro, with a capital of the same name. Thus, with its length of just over 13 kilometers, the bridge marked the beginning of a new era that deepened the political, economic, and social integration of the two territories.