Rancagua (rängkäˈgwä, –käˈwä) [key], city (1990 est. pop. 190,400), capital of Libertador General Bernardo O'Higgins region, central Chile, in a fertile valley among the Andean foothills. One of Chile's largest copper mines (El Teniente) is nearby. Rancagua's industries include food processing, automobile manufacture, and ore refining. The city was founded in 1743. At Rancagua on Oct. 1 and 2, 1814, Bernardo O'Higgins led a defense of the plaza against a superior Spanish royalist force in an engagement that closed the first phase (1810–14) of the Chilean war against Spain.