When Ecuador split off from Gran Colombia in the nineteenth century, it signed a border agreement with Peru, defining its boundaries along the Maranon River. In 1941, Peru invaded Ecuador and occupied half the country for ten days. Afterwards, a peace treaty was brokered and guaranteed by the United States, Brazil, Argentina, and Chile. The United States mapped the border, leaving approximately 48 miles (78 kilometers) of a line in the Cordillera del Condor area unmarked. The area became a site for dispute in 1941, and again in 1995.