The argument was over which way the water flowed. Because Lácar Lake drains west into the Pacific rather than east across the Andes, Chile contended that this whole valley should be Chilean. Argentina answered the only way borders were settled in 1898: it sent soldiers. On 4 February of that year, a military expedition under Colonel Celestino Pérez founded a frontier outpost on the lake's eastern shore to make the claim permanent. That outpost became San Martín de los Andes, and the town still carries the geometry of that decision, a settlement built to hold a line that nature seemed to have drawn the other way.
From its founding as a garrison, San Martín de los Andes filled with people from elsewhere. Spaniards, Italians, Germans, Dutch, and French arrived; Syrian-Lebanese merchants opened shops; settlers drifted over the passes from neighboring Chile. They blended with the people already living in the valley, and the town was diverse from its first years, a quality you can still read in its surnames, its old family stores, and its food. Growth came slowly, then steadily. The 1970 census counted just over six thousand residents; by 2010 the population had climbed to nearly thirty-six thousand, making it one of the more populous towns in the province of Neuquén and one of the fastest-growing.
San Martín de los Andes was deliberately shaped to look like a mountain village, raised from the region's own materials: stone, timber, and shingled roofs. A handful of early buildings still anchor the town's memory, among them the First Post Office of 1899, the Old Lácar Hotel of 1910, the Primeros Pobladores Museum building of 1911, and the old Chidiak general store dating to 1938. When the creation of Lanín National Park restricted the cutting of local wood, a second architectural era arrived, bringing taller two-storey houses, the national park's administration building of 1946, and a town hall completed in 1960. The effect is a coherent alpine townscape, less invented than grown.
For its first decades the town lived on wood logging and raising livestock. That changed in 1937 with the opening of Lanín National Park, after which tourism steadily displaced the older trades; logging shrank to a minor activity, still providing a few local jobs. Today San Martín de los Andes serves as the administrative seat of Lanín National Park and the gateway to the southern Neuquén highlands, including Nahuel Huapi National Park and the ski mountain of Cerro Chapelco. It is a four-season resort. In summer the surrounding country offers hiking, mountain trekking, rafting, and fishing; in winter, Chapelco draws skiers and snowboarders, and has hosted FIS Snowboard World Cup competition.
The town keeps a full calendar of its own traditions. The National Mountainman Festival and the Trabún Festival both celebrate local mountain culture, and San Martín hosts the South American Bird Fair, billed as the continent's main gathering of birders, fitting for a place ringed by national parks. Its setting near the frontier still defines daily life: several Andean passes lead into Chile, and the Hua Hum pass, just 45 kilometers away, drops toward Panguipulli, where the road simply ends and a ferry carries travelers across Lake Pirihueico because no road has ever been built through that stretch of forest. More than a century after soldiers came to settle an argument, the border remains the town's nearest, wildest neighbor.
San Martín de los Andes lies at roughly 40.17°S, 71.35°W in Argentina's Neuquén Province, on the eastern end of Lácar Lake at the foot of the Andes. From the air, the town sits where the long, fjord-like Lácar Lake meets the mountains, with the ski runs of Cerro Chapelco to the southeast and, on clear days, the conical peak of Lanín volcano prominent to the north. Recommended viewing altitude 7,000 to 10,000 feet. The town is served by Aviador Carlos Campos Airport (ICAO SAWO), about 22 km away and the main airport of southern Neuquén; Bariloche (SAZS) lies to the south. Strong westerly winds spill over the cordillera, so calmer morning conditions are best for approach and sightseeing.