In 1897, the Brazilian army mobilized to crush Canudos, a utopian community founded by a millenarian preacher in the country’s remote northeast, near Monte Favela. The soldiers had been promised land for their service. But no reward awaited them when they returned to Rio de Janeiro, so they settled on a hillside, first in tents and then in improvised shacks. Soon their community became known by the name of the mountain where they had fought.

This is how Brazil’s poor urban neighborhoods came to be called “favelas” — but these communities, today home to over 16 million people, emerged from a rural exodus that predates the Canudos soldiers and continues into the present. The first decisive event was the abolition of slavery in 1888, which sparked a large migration of freed agricultural laborers to cities without the low-income housing stock to absorb them. The second boom started after World War II and continued into the 1970s, as the government invested heavily in urban industrialization. With the agricultural sector falling behind and land reform nowhere on the horizon, the rural poor set off for the cities — where, again, housing was in short supply.

After suffering an economic crisis in the 1980s, Brazil saw urbanization without growth. As millions piled into the cities, favela conditions became increasingly desperate; drug traffickers took over the neighborhoods, and the homicide rate spiked. “Starting as early as 1982, things became different,” a favela resident told the researcher Janice Perlman. “That is when the factories started to close one after another and when the traffic started.”