Premise: The Salta–Antofagasta railway, also named Huaytiquina, is a non-electrified single track railway line that links Argentina and Chile passing through the Andes. It is a railway with a total length of 941 km (571 in Argentina and 330 in Chile), connecting the city of Salta (Argentina) to the one of Antofagasta (Chile), on the Pacific Ocean, passing through the Puna de Atacama and Atacama Desert.
Hypothesis: The Salta–Antofagasta railway wasn't always a single track railway line.