The lands where Rio Branco now sits were once home to the Aquiri, Canamari, and Maneteri peoples. The rubber tappers who arrived in the late 19th century were mostly Brazilians - drawn west by the rubber boom, working the hevea trees of what was then technically Bolivian territory. Villa Rio Branco became the main urban center of the Acre valley by August 1904, in the immediate aftermath of the Treaty of Petropolis that made Acre Brazilian. Around the Gameleira tree, the streets filled with bars, cafes, casinos, and the commercial agents of international trading houses moving thousands of contos de reis in rubber transactions. The city was one of the oldest in Brazil's interior - older than Goiania, Belo Horizonte, Brasilia, Palmas, or Boa Vista - and during the boom years it was wealthy in a way that was hard to sustain once synthetic rubber ended the monopoly.

Rio Branco sits at 143 meters above sea level, straddling both banks of the Acre River. The political administration was eventually moved to the left bank - higher ground, less prone to flooding - while the original commercial zone on the right bank gradually declined. By the 1930s, Syrian and Lebanese immigrants had given that area a new life; one neighborhood became known as Bairro Beirut. By the 1950s the old commercial core had faded into what locals call the Second District. Today six bridges link the two districts, the newest being the Joaquim Macedo Catwalk, a cable-suspension pedestrian bridge finished in 2006. Rio Branco also has the largest proportional bicycle path network per inhabitant of any Brazilian state capital, a fact the city likes to mention.

The climate is tropical monsoon, and most of the year the weather does what you would expect near nine degrees south: hot, humid, with heavy rain from October through May and a shorter dry season from June to September. Rio Branco has the lowest average annual temperature of any Amazon or Northeast Brazil capital, but lowest here still means daytime highs in the upper twenties. The exceptions are what make the climate interesting. In July 2010, a cold front from the south pushed temperatures to 9.8 degrees Celsius at dawn on the 19th - nearly freezing in a city where 22 degrees is considered cool. And the Acre River, which the city depends on for transport and atmosphere, has many floodplain stretches that submerge the lower neighborhoods when the rains run hard. In March 2023, over 15,000 people were displaced after a single month delivered 585.9 millimeters of rain.

One of Rio Branco's most unusual landmarks is the tomb of Raimundo Irineu Serra, the rubber tapper from Maranhao who moved to Acre and founded the religion now called Santo Daime. His sepulcher sits in the Alto Santo neighborhood and has become a pilgrimage site for Daimistas around the world. Santo Daime is the religion built around a tea brewed from ayahuasca and chacruna - a sacrament consumed in hours-long ceremonies, wrapped in Catholic hymns and the local cosmology of the forest. Its global reach is small but remarkable, with communities from Amsterdam to Japan tracing their practice back to this quiet corner of the Amazon capital.

Historically the economy depended on two forest products: natural rubber and brazil nuts. Today wood is the main export of the state of Acre, along with acai fruit, cassava flour, copaiba oil, and beef. Rio Branco is trying to reinvent itself through agribusiness, aquaculture, and ecotourism; Petrobras has suggested the region has potential for future petroleum extraction, though nothing has been developed at scale. The city hosts the Federal University of Acre, the only public university in the state. The airport on BR-364 handles domestic traffic and occasional international flights; the road network connects east to the rest of Brazil and west to Peru via the Interoceanic Highway, which links Rio Branco all the way to Cuzco. It is still a city you have to want to reach - but one that connects, if you follow its roads far enough, two coasts and three languages.