The railway started at the Chilean port of Antofagasta. It proceeded up the front range of the Andes to Ollagüe on the Bolivian border, then across the Bolivian pampas to Uyuni and Oruro. At Oruro, the gauge changed to 1,000 mm (3 ft 3 3⁄8 in) metre gauge for the remainder of the route to La Paz, the capital of Bolivia. A number of branches were added to reach various mining fields. The
Collahuasi branch reached 4,815 m (15,797 ft) above sea level, regarded at the time of construction as the highest railway in the world. The total length of the 2 ft 6 in (762 mm) gauge lines, including branches and subsidiaries, was 1,537 km (955 mi).