“Usumacinta River: River, southeastern Mexico and northwestern Guatemala. Rising in western Guatemala, it flows northwest, forming a section of the Guatemala-Mexico boundary, before emptying into the Grijalva River in Mexico. Its upper course is known as the Chixoy or Salinas River; with the Chixoy, it is approximately 600 miles (1,000 kilometers) long.”
Excerpted from: Stevens, Mark A., Ed. Merriam-Webster’s Collegiate Encyclopedia. Springfield, Massachusetts: Merriam-Webster, 2000.