The river's sources are located in the Sierra Madre just north of Cajolá where it is called Río Blanco.

The Cuilco follows its largely northward course through San Marcos, and Huehuetenango, crossing the border with Mexico at 15°26′03″N 92°06′24″W / 15.434156°N 92.106800°W / 15.434156; -92.106800 (Río Cuilco), continuing its course northwards into the Presa de La Angostura, one of Mexico's largest artificial lakes.

The Cuilco river basin covers an area of 2,274 square kilometres (878 sq mi) in Guatemala.

This article related to a river in Guatemala is a stub.

You can help Wikipedia by expanding it.This article related to a river in Mexico is a stub.