The company was founded in 1887 to take over and complete two lines from Monte Caseros in Corrientes Province. The first was to go to Corrientes (371 km), the provincial capital, and the second to Posadas (442 km), the capital of Misiones Province.
Construction of the line to Corrientes, completed as far as Curuzú Cuatiá in 1890, was extended to Mercedes in 1898 and finally reached Corrientes later in the same year. The Posadas line reached Paso de los Libres in 1894 and was extended to Santo Tomé in 1901. Once the section from Santo Tomé to Posadas was opened some years later in 1911 an international rail connection with Paraguay was established.
Two years later a branch line from San Diego to the port of Goya on the River Paraná was completed and in 1915 the line from Concordia was extended south to the river port of Concepción del Uruguay. Later that same year the ANER established a joint administration with the neighboring British-owned Entre Ríos Railway.
By the time then President of Argentina Juan Perón nationalised the complete Argentine railway network in 1948 the ANER was operating a 1,212 km network which became part of the state-owned General Urquiza Railway.