This book, "Directory of Illinois mineral operators, to accompany mineral industries map, September 1, 1920 (1921)", by Illinois State Geological Survey, Christensen, H. P. (Henrietta Petrea), is a replication of a book originally published before 1921. It has been restored by human beings, page by page, so that you may enjoy it in a form as close to the original as possible. This book was created using print-on-demand technology. Thank you for supporting classic literature.