He held the position throughout the term of four presidents of the republic - the governments of Rodrigues Alves, Afonso Pena, Nilo Peçanha and Hermes da Fonseca - forming a national unanimity in their time.

This was due to being a convinced monarchist and to honor his late father, the senator and diplomat José Maria da Silva Paranhos, Viscount of Rio Branco.

Being a monarchist, however, was no impediment for his success as a diplomat: the Baron of Rio Branco reached the heights of his career during the Republic, when he acted as Minister of Foreign Affairs for 10 years and settled all of Brazil's remaining border disputes by peaceful means.

His death, during the carnival of 1912, altered the calendar of the popular feast that year due to official mourning and great tributes in his honor in the city of Rio de Janeiro.

Rio Branco's most important legacy to Brazil was his successful effort, as Minister of Foreign Affairs, in defining the country's borders with all of its neighbours.

He is considered one of the most prominent Brazilian statesmen ever, as his proverbial work capacity, knowledge and skills were essential for the successful outcome of difficult boundary disputes, some of which submitted to international arbitration – such as with Argentina and France –, as well as for incorporating new territory (the state of Acre, originally Bolivian).

On those occasions, he never abandoned his belief in diplomacy as the means to handle international matters, thus helping establish Brazil's reputation as a peace-loving nation.

In 1903 Rio Branco signed the Treaty of Petrópolis with Bolivia, putting an end to the dispute involving the present Brazilian state of Acre.

For this reason, he was honored by the government of Uruguay, and his name was given to the old Pueblo Artigas, now the city of Río Branco, in the department of Cerro Largo, near the Brazilian Jaguarão.

In 1908, then in Rio de Janeiro, he invited the engineer Augusto Ferreira Ramos to design a cable car system that would facilitate access to the summit of Morro da Urca, known worldwide as the Sugar Loaf.

He was very popular, however, among the people; at the time of his death, to the point of paralysing Carnival – another unparalleled feat in Brazilian history – on the day he died (February 10), when official mourning was declared.