The Usumacinta River is a river in southeastern Mexico and northwestern Guatemala. It is formed by the junction of the Pasión River, which arises in the Sierra de Santa Cruz (in Guatemala) and the Salinas River, also known as the Chixoy, or the Negro, which descends from the Sierra Madre de Guatemala. It defines part of the border between the Mexican state of Chiapas and Guatemala, then continues its northwesterly course, meandering through the Mexican state of Tabasco to the Gulf of Mexic… (More on Usumacinta)