The name comes from the mantled howler monkey, locally known as Congo monkey, as it is common to find it in the region and its howling can be heard at great distances. The name was in use by the 19th century.
Physical aspects
The Congo volcano is a stratovolcano, with an area of 25 km2, 6 km north of Poás Volcano. The crater is open on its north side, and it is very eroded due to rain, which in turn provides the source for María Aguilar river and its valley.
References
^Alvarado Induni, Guillermo. Los volcanes de Costa Rica. Editorial de la Universidad Estatal a Distancia. pp. 196–197. ISBN978-9968-316-79-8.