For the first years, ore was taken down the mountainside by cart as far as Graneros, where it was loaded onto a train for transport to the port of Valparaiso and international destinations. A narrow gauge railroad line between Sewell and Rancagua was started in 1907 and fully in use by 1911. This became the only way in and out of the mining camp for personnel and goods. (photo). With better transportation, the mining camp became more efficient and profitable.
In 1915 the camp was named Sewell, in memory of Barton Sewell, the first president of Braden Copper. The camp continued to grow, with the construction of a hospital, a model for the time, a fire department and a social club as well as a new smelter and other industrial buildings. (photo). In 1916. Kennecott Copper Company acquired Braden and retained ownership until 1967.
World War I created a huge demand for copper and the mine responded. It grew to hold 14,000 inhabitants in 1918 with an accompanying growth of housing, social services, entertainments and cultural facilities. In 1921, smelting operations moved to Caletones, about 4 miles (6 km) downhill. Photo of the Caletones Copper Smelter .
Business functions clustered around the staircase leading up from the railroad station, and over time the staircase became known as the Escalera Central. Over the next decades, residential areas appeared, with housing for married workers and families. Playgrounds, plazas, movie theater, small shops and businesses, schools and other buildings were erected in what was becoming a definite plan. There was no vehicular traffic beyond the railroad which stopped at the station. Pedestrian traffic went up and down vertical staircases and unpaved horizontal streets and paths. All goods were carried up to various destinations by porters, called Cargadores. Campamento Americano, or the residential section for foreign personnel, grew on the west-facing slope of Cerro Negro.
Structures were built into the sides of the mountain, according to the topography. Most of the houses were of wood, two or three stories high, narrow and long. Some were more substantial, built of stucco, but all buildings, industrial, commercial or residential with threatened by earthquakes, avalanches and explosions. Despite these dangers, Sewell flourished and reached its zenith in the 1960's with 16,000 inhabitants.
In 1967, the Chilean government obtained fifty-one percent of the company and things changed quickly. The population of Sewell and Caletones was moved to Rancagua and the surrounding area, and the Carretera de Cobre, or Copper Highway, (Approach by Carretera de Cobre) was built for commute purposes. By now the mine had reached levels so deep in the mountain that a train tunnel built into the side of the mountain near Rancagua could transport the miners to their stations without having to descend from the top of Cerro Negro.
In 1971, following nationalization, ownership of the mine was turned over to CODELCO, the state-owned producer of copper, and the mine renamed El Teniente. By 1977, there were less than 2000 people living there and in the early 80s, the demolition of Campamento Americano and other buildings left the camp only the basic structures needed for mining.
Sewell became almost a ghost town. In recent years, Codelco has maintained certain sections for historical and tourism, with a number of buildings used for offices and other mining business.