| 1. |  | Illinois-Wisconsin, Grays Lake quadrangle : topography | Illinois; Maps; Topographic maps; Topography; Grays Lake (Ill.); Wisconsin | 1 map : col.; Relief shown by contours and spot heights.; "Surveyed in 1919-1920."; "Surveyed in cooperation with the States of Illinois and Wisconsin."; "Contour interval 10 feet." |
