This book was first conceived as being devoted entirely to descriptions of the maps produced by the U.S. Geological Survey. As the project developed, however, it became clear that the story of maps is not complete unless
it is properly set in the background of the American mapping effort as a whole. Extension of the scope of the book does not preclude placing emphasis on the Geological Survey mapping program, which is treated in full while other programs are treated only in sufficient detail to provide leads for exploring them elsewhere.