Master Naturalist Paul Rieger holds up a bison hoof during his presentation at the Sterling-Rock Falls Historical Society's meeting Sunday afternoon at the Lincoln Learning Center in Sterling. Rieger talked about the history of bison in the area and Nachusa Grasslands' role in restoring their numbers. Master Naturalist Paul Rieger shows a photo of the new visitors center at Nachusa Grasslands on Sunday during his presentation at the Sterling-Rock Falls Historical Society's meeting. The audience listens Sunday as Master Naturalist Paul Rieger discusses the toll that farming and westward settlement took on grasslands and bison, and how that changed the American landscape. Master Naturalist Paul Rieger speaks Sunday at the Sterling-Rock Falls Historical Society's meeting at the Lincoln Learning Center in Sterling.