The period following the Civil War naturally became one of national expansion, the faces of many were turned westward, and exploration of the national domain for its industrial possibilities took on fresh interest. Home-seekers and miners largely made up this army of peaceful invasion, and the winning of the West began on a scale quite different from that of the days of the military path-finding expeditions of Fremont and other Army officers. Thus the nation was aroused to the task of investigating its public lands and Congress gave the support needed to make geologic exploration possible on a large scale. Geologic surveys of a high order were continued in the older States, as shown by the contributions during this period of J. P. Lesley and G. H. Cook in the East, W. C. Kerr, E. W. Hilgard, and E. A. Smith in the South, and J. S. Newberry, C. A. White, Raphael Pumpelly, T. C. Chamberlin, Alexander Winchell, and T. B. Brooks in the Central States. To the north the Canadian Survey, organized in 1841 under Logan, had continued under the same sturdy leadership until 1869, when the experienced and talented Doctor Selwyn became Director. As contrasted with the short careers of most of the State Surveys and with the temporary character of all of the Federal undertakings in geologic investigation, the continuance of the Canadian Geological Survey for more than half a century under two directors gave opportunity for continuity of effort in making known to the people of the Dominion its resources and at the same time contributing to the world much pure science. Passing with simple mention the two Government expeditions into the Black Hills, which afforded opportunity for geologic exploration by N. H. Winchell in 1874 and by Jenney and Newton in 1875, the record of geologic work under Government auspices in the period immediately following the Civil War groups itself around the names of four leaders—Hayden, King, Powell, and Wheeler. The four organizations, distinguished commonly by the names of these four masterful organizers, occupied the Western field more or less continuously from 1867 to 1878, and the sum total of their contributions to geography and geology was large indeed. In the words of Clarence King,[101] “Eighteen hundred and sixty-seven, therefore, marks, in the history of national geological work, a turning point, when the science ceased to be dragged in the dust of rapid exploration and took a commanding position in the professional work of the country.” Together these four expeditions covered half a million square miles, or more than a third of the area of the United States west of the one-hundredth meridian, and the cost of all this work was approximately two million dollars, which was a small fraction of its value to the nation counting only the impetus given to settlement and utilization.