In 1900 two British-owned companies were operating railways in Patagonia; the Central of Chubut metre gauge, 1,000 mm (3 ft 3 3⁄8 in) , line between Puerto Madryn and Trelew and the Buenos Aires Great Southern broad gauge line between Bahía Blanca and Neuquén. During the presidency of José Figueroa Alcorta, the Argentine government devised a plan in 1908 to populate Patagonia by constructing two additional broad gauge, 5 ft 6 in (1,676 mm), railway lines in that part of the country. The first line one was to run from San Antonio Oeste, in Rio Negro Territory (later to become Rio Negro Province), via Valcheta to Nahuel Huapi Lake, and the second from Puerto Deseado via Colonia San Martin to a junction with the first line. The second line was to have branches to Comodoro Rivadavia, via Sarmiento, to Colonia 16 de Octubre and to Buenos Aires Lake.
The line from Puerto Deseado, started in 1909, was built only as far as Las Heras, a distance of 283 km, and a 197 km line from Comodoro Rivadavia to Sarmiento was completed. These lines came under the administration of Ferrocarriles del Estado in 1914. Meanwhile the line from San Antonio Oeste, started at the end of 1908, reached Km 217 in 1911 and Maquinchao two years later. In 1916 this line also came under the administration of Ferrocarriles del Estado, was extended to Ingeniero Jacobacci in 1917 and to Bariloche in 1934.
In 1946 a 402 km long narrow gauge, 750 mm (2 ft 5 1⁄2 in) , branch line was opened from Ingeniero Jacobacci to Esquel in Chubut Province and became known affectionately as La Trochita.