William Braden was educated at MIT and started his career in Montana. He was sent by his employer to Chile in 1894 to oversee the erection of some mining equipment at an International Mining Exposition and to check on the possibilities of mining operations in Chile. There he met Marco Chiapponi, an Italian mining engineer, who nine years later (1903) called his attention to an abandoned mine known as “El Teniente.” Braden returned to Chile, liked what he saw, and returned to the United States to find financial backing. E.W. Nash and Barton Sewell, President and Vice President of American Smelting, as well as other prominent mining men, provided initial financial backing. Braden Copper Company was organized in Maine in 1904. This endeavor survives today as the El Teniente division of CODELCO, and El Teniente remains the world's largest underground copper mine.
Braden's namesake operation has been one of the world’s leading copper producers for almost a century. Development of El Teniente was challenging. In addition to mine and plant development, it required construction of a 35-mile road; a town, complete with stores and housing; a concentrator; aerial tramways; and a hydroelectric power plant. Soon, it became apparent that a railroad and smelter would also be needed. Braden built a small smelter that produced matte for shipment, despite expert opinion that it could not be done, obtaining these results with minimal money and without elaborate equipment.
About this time, one of the original backers died, and the Guggenheims bought control of the company, assuming control in June of 1909. William Braden retired from active management of Braden Copper in 1910 but retained a seat on the board of directors. Newly founded Kennecott Copper, also controlled by the Guggenheims, took control of the mine in 1915. After relinquishing active management of Braden Copper, Braden sent a 25-ton sample of El Teniente ore to London in 1911 for testing by the Minerals Separation Company. At the time, it was thought that chalcocite was not amenable to flotation; however, testing produced excellent recoveries.
As a result, Braden Copper became the first copper producer of any significance to use flotation to scavenge additional copper from the tailings of a gravity concentrator. Braden then began to examine other properties. His next success was the Potrerillos mine in northern Chile. In 1912, Braden examined the area, which had numerous old mines, and saw the possibility of a large-scale porphyry deposit. He invested in churn drilling and soon had enough ore reserves to interest Anaconda. Anaconda organized the Andes Mining Co. to develop and operate Potrerillos. This property faced the same challenges as El Teniente, and production did not start until 1927.
Braden’s name is also associated with the discovery of Los Pelambres and Lo Aguirre, major Chilean porphyry copper deposits that were explored and drilled by Braden but developed by others many years after his remarkable life.