1909 Geological Map of Ohio, by John A. Bownocker. 31 x 33-inch format, scale 1 in. = 8 mi. (1:500,000). The 1909 geologic map was the first to recognize the Ordovician System in Ohio. It identifies 11 geologic units and also features oil and gas fields, salt works, gypsum mines, and Portland cement works, along with other new geologic information. This map does not have a cross section.