Chacabuco Nitrate Works was built between 1922 and 1924 by the Anglo Nitrate Company. It was the last nitrate works to introduce the Shanks production system. It was notable for its size, production capacity and the quality of its installations. It went out of business in 1940. In 1971 it was declared a national monument and from 1973 to 1974 it was used by the Pinochet regime as a concentration camp for political prisoners.

https://en.wikipedia.org/wiki/Chacabuco