The first train ran on July 2, 1889, hauling freight and passengers from Córdoba toward Cruz del Eje. It belonged to the Córdoba North Western Railway, one of the British-owned companies that laced Argentina with steel rails in the boom decades before the world wars. Ownership changed hands the way fortunes did in that era: the Córdoba Central Railway took the branch in 1901, the Argentine State Railway absorbed it in 1909, and in 1948 Juan Perón nationalized the entire network, folding the old British line into the sprawling General Belgrano Railway. The technical name survives today as the unglamorous "A-1" branch, a bureaucratic label for one of the most scenic rides in the province.

The 1960s were the line's golden age. Trains arrived crammed with holidaymakers from Córdoba, Rosario, and Buenos Aires, all bound for the resort towns strung along the Punilla Valley at fares cheap enough that ordinary families could afford the mountains. The Sierras Chicas rose green on either side, and the stations themselves became destinations. Then the economics turned. Argentina's railways bled money for decades, and in 1977 the service simply stopped. The handsome stone depots fell quiet. The Valle Hermoso station, once full of arriving tourists, would eventually be reborn as a cultural center, its platforms hosting art instead of passengers.

The 1990s brought a peculiarly Argentine experiment. Under President Carlos Menem's privatization drive, the line passed to Grupo Alcázar, a consortium whose previous ventures included running the Córdoba Zoo and a racetrack. Trading under the name Aero Ruta, they revived the route as a tourist service and gave it the name it still carries: Tren de las Sierras, train of the mountains. The romance lasted barely a few years before service abruptly halted in 2001. Three years on, the provincial government revoked the concession outright, citing neglected track and a service allowed to crumble. For the second time in a generation, the line lay dead.

Resurrection came in 2007, when the state poured ten million dollars into reopening a short stretch between Rodríguez del Busto and La Calera. Diesel-electric cars, built in Portugal and rebuilt in workshops at Chascomús, returned to the rails. The route crept forward year by year, reaching Cosquín through the dramatic Quebrada of Bamba gorge. The recovery was not without its bruises. When Alta Córdoba was made the terminus in 2009, the operator soon retreated again because residents of poor neighborhoods near the tracks were throwing stones at passing trains, a quiet measure of the inequality the railway runs through. In 2013 the state operator Trenes Argentinos took over, and in November 2023 the line finally pushed all the way to Capilla del Monte, reuniting the city with the far valley for the first time in decades.

Today three morning trains leave Alta Córdoba bound for Cosquín, with departures returning through the afternoon. End to end, the journey runs two hours and twenty-four minutes, which is rather the point. This is not transport for the impatient. The reward is the unhurried unspooling of the Punilla Valley through the window, the same view that drew the crowds of the 1960s, now experienced at a pace that lets you actually see it. Few railways anywhere have been pronounced dead so often and kept arriving anyway.