While Powell is most widely known as the first explorer of the Colorado River, he also made significant contributions as an administrator and as an advocate for conservation and careful planning in the use of western lands. He argued that because of their arid nature, western public lands should be classified as to their potential use for irrigation, pasturage, timber, and mineral or coal extraction. Powell also maintained that the traditional 160-acre farm as provided for in the Homestead Act was much too small for grazing purposes in the West. Instead, grazing farms there should be expanded to no less than 2,560 acres in order profitably to support herds.
His principal publications were: Exploration of the Colorado River of the West and its Tributaries (1875), which was revised and enlarged as Canyons of the Colorado in 1895; Report on the Geology of the Eastern Portion of the Uinta Mountains (1876); Report on the Lands of the Arid Regions of the United States (1879); Introduction to the Study of Indian Languages (1880); and Truth and Error, or the Science of Intellection (1898).