Elliot described his aims for this work in the preface:
"Since the time of Wilson and Audubon, no work has been published upon American Ornithology, containing life-size representations of the various species that have been discovered since the labors of those great men were finished. The valuable productions of Cassin, as well as the revised edition of the ninth volume of the Pacific Rail Road Report, the joint labor of Messrs. Baird, Cassin and Lawrence had indeed appeared...but no attempt had been made to continue the works of the first great American naturalists in a similar manner [i.e. with the birds represented full-size where possible]....It was, therefore, with the desire to contribute...towards the elucidation of the comparatively little known species of the Birds of North America, their habits and economy, as well as to render their forms familiar so far as life-size representation of them might serve to do, that I undertook the present publication."
The work includes 72 handcolored lithographed plates, including 55 by Elliot, and 15 by Joseph Wolf (1820-1899).
Digital facsimile of the 1869 issue from Biodiversity Heritage Library at this link.