North of this elevation, which formed the southern shore of the ancient Mojos Lake, are the llanos of Guarayos and Mojos, occupying an extensive region traversed by the Guapore, San Miguel, Guapay, Mamore, Yacuma, Beni and Madre de Dios rivers and their numerous tributaries.
It was once covered by the great Mojos Lake, and still contains large undrained areas, like that of Lake Rojoagua (or Roguaguado).
The Indian population (920,860) is largely composed of the so-called civilized tribes of the Andes, which once formed part of the nationality ruled by the Incas, and of those of the Mojos and Chiquitos regions, which were organized into industrial communities by the Jesuits in the 17th century.
The Mojos and Chiquitos tribes, also, have been less prosperous since the expulsion of the Jesuits, but they have remained together in organized communities, and have followed the industries and preserved the religion taught them as well as circumstances permitted.
The Jesuit founders of the Mojos missions took cattle with them when they entered that region to labour among the Indians, with the result that the Mojos and Chiquitos llanos were soon well stocked, and have since afforded an unfailing supply of beef for the neighbouring inland markets.