This index is based upon the occupational designations returned on the schedules at the Twelfth, Thirteenth, and Fourteenth Censuses of the United States. It has been supplemented, however, by designations gleaned from various occupational glossaries and from other sources.

The index is printed in two forms—classified and alphabetical—a separate volume being devoted to each form.

In this classified index the occupational designations are arranged in classified form, each under its proper occupation or occupation group.