Chascomús, is the principal city in Chascomús Partido in eastern Buenos Aires Province in eastern Argentina, located 123 km (76 mi) south of the capital Buenos Aires. As of 2001, the city had a population of 30,670 people.
The city was founded as a fort (the Fortín de San Juan Bautista) on May 30, 1779, by Captain Pedro Nicolás Escribano, head of the Blandengues Cavalry. The city was the site of a 1839 rebellion against the dictatorial regime of Governor Juan Manuel de Rosas; the uprising, known as the Libres del Sur ("Freemen of the South") ended in defeat following a battle on November 7. The Buenos Aires Great Southern Railway line arrived at the town in 1865, and Chascomús was recognized as a city and department by the Provincial Legislature in 1873.