This is an extremely important account of the original people in the New World, and documentation of black people prior to Columbus. Bancroft had become deeply conscious of the history of America and the native races, the establishment of European civilization on American shores, influences on original inhabitants, and the resulting mixture of races and cultures. Bancroft made this theme a major feature of his histories. In 1874-1875, he published five volumes on Native Races. These volumes were succeeded by three on History of Central America (1882-1887), and two on North Mexican States and Texas (1883-1889). Such massive works required an abundance of source materials, few of which were available until Bancroft undertook to collect them.

He did a remarkable amount of field work. In 1883, for example, he went to Mexico to meet its leaders, particularly ex-president Porfirio Díaz and his successor, President Manuel González. Bancroft also employed local agents in these countries to help him acquire the materials indispensable for the writing of his ambitious works.