cabecera (county seat) and partido (county) of Gran (Greater) Buenos Aires, eastern Argentina. It lies immediately northwest of the city of Buenos Aires, in Buenos Aires provincia (province). The county seat and county began as an early rural settlement centred on the 18th-century Chapel of Santos Lugares. In 1856 the settlement was formally declared a town, and eight years later the county of San Martín (named for the Argentine liberator) was created. In 1911 General San Martín town was given official city status, and since then it has grown into a major industrial centre, processing and manufacturing linseed oil, textiles, dairy products, frozen meat, cigarettes, liquor, and a variety of other products.

With the growth of the national capital, General San Martín has been absorbed into Gran Buenos Aires. Pop. (2001) city, 25,781; county, 403,107.