Powell's first expedition was designed as an exploration to cover ten months, part of which was to be in winter quarters; circumstances reduced the time to three.

It was also more or less of a private venture with which the Government of the United States had nothing to do.

It became necessary to supplement it then by a second expedition, herein described, which Congress supported, with, of course, Major Powell in charge, and nominally under the direction of the Smithsonian Institution, of which Professor Henry was then Secretary and Professor Baird his able coadjutor, the latter taking the deeper interest in this venture.

Powell reported through the Smithsonian; that was about all there was in the way of control.
The material collected by this expedition was utilised in preparing the well-known report by Major Powell, _Exploration of the Colorado River of the West, 1869-1872_, the second party having continued the work inaugurated by the first and enlarged upon it, but receiving no credit in that or any other government publication.
As pointed out in the text of this work, a vast portion of the basin of the Colorado was a complete blank on the maps until our party accomplished its end; even some of the most general features were before that not understood.

No canyon above the Virgin had been recorded topographically, and the physiography was unknown.