43 U.S.C. § 42

The Director of the United States Geological Survey is authorized and directed, on the approval of the Secretary of the Interior, to dispose of the topographic and geologic maps and atlases of the United States, made and published by the United States Geological Survey, at such prices and under such regulations as may from time to time be fixed by him and approved by the Secretary of the Interior; and a number of copies of each map or atlas, not exceeding five hundred, shall be distributed gratuitously among foreign governments and departments of our own Government to literary and scientific associations, and to such educational institutions or libraries as may be designated by the Director of the Survey and approved by the Secretary of the Interior. On and after June 7, 1924 , the distribution of geological publications to libraries designated as special depositaries of such publications shall be discontinued.