The territory of the Guerrero people covered part of the southwest coast of modern-day Mexico and was flanked by the Western Sierra Madre. The region consists of both large and small valleys that are quite isolated from each other, making communications between them difficult. It is also an area of frequent seismic activity and landslides. The coast and river valleys provided the resources needed to populate and sustain the region. The Guerrero people were not a specific culture, but rather a number of groups that, in different periods and in different parts of the region, shared certain characteristics.