Portuguese explorer Gaspar de Lemos reaches the Bay of Guanabara in Brazil on January 1, 1502 and mistaking the bay's entrance for a river, named it "Rio de Janeiro" (River of January). The name was given to honor the month of their arrival.
The name stuck for the bay and eventually that eventually developed there. Lemos was part of a larger Portuguese expedition led by Amerigo Vespucci that explored the coast.
