April 7, 2025 · Leandro Scheurle
Captain José León Lemos and his detachment of 55 soldiers crossed the Portillo and Piuquenes passes in January and February of 1817 as part of the Army of the Andes, one of the 6 armies that crossed the Andes, from southern Mendoza to La Rioja, in that historic feat and colossal strategic undertaking known as the Crossing of the Andes, led by General José de San Martín. This particular crossing was part of one of José de San Martín's strategies to liberate Chile.
Lemos set out from San Carlos in September of 1816, taking advantage of the start of the thaw, in order to scout and survey the possible route for the definitive crossing.
"It has not been possible to determine the exact day the detachment crossed the mountain range. The first communication received by the intendant of Cuyo is dated February 7th at Peñón Rajado, near Laguna Negra along the Río Yeso gorge; in it, they reported that on that same day the army had attempted to surprise the San Gabriel guard post (Chile) but had failed in the attempt due to a storm; the royalist guard had abandoned the post and fled. Having accomplished its mission of making itself noticed and giving the impression of an invasion, the attacking force withdrew."
Lemos then camped at Los Piuquenes (Chilean territory) and later joined up with San Martín.
All historians agree that this was one of the most important armies and geographic crossings when it came to making San Martín's entire army's efforts count. 
Today, Paso Portillo (entirely on the Argentine side) is a place of great historical and scenic value. The "Huella Turística Cruce de los Andes Paso Portillo" trail is a popular tourist route, and today it's used, on horseback and on foot, to follow the very same route General Lemos's Army once took. In fact, some guides and baqueanos tell us, year after year, that in some of the side valleys off the great Río Tunuyán valley (near the Real de la Cruz military refuge site) bayonet-fitted rifles and other weaponry from that immortal era have occasionally been found.
Today it's possible to book agencies and professional services that will take you to cross the Andes along the very same route taken by the Army of the Andes, led by General Lemos, between Manzano Histórico (Tunuyán, Mendoza) and El Yeso (Chile), passing through Paso Portillo and Piuquenes (the border marker). In a week you'll walk more than 80 km, accompanied by horses and professional guides, tents and the best food, starting with transportation from the city of Mendoza and ending, also with additional transportation, in Santiago, Chile.
Here's the program: ANDES CROSSING TREK - LEMOS - PORTILLO - PIUQUENES
