Europeans "discovered" America only in the sense that earlier they didn't know it was there. The Native Americans certainly knew. Chapter 1 provides a fine summary of major pre-Columbian Indian cultures in North America. You may wish to expand on one or more of these societies through lecture. See, for example, Lynda Norene Shaffer, Native Americans Before 1492: The Moundbuilding Centers of the Eastern Woodlands (1992), or Susan L. Woodward and Jerry N. McDonald, Indian Mounds of the Middle Ohio Valley: A Guide to Adena and Ohio Hopewell Sites (1986), or Jon Muller, Archaeology of the Lower Ohio Valley (1986), or Ronald J. Mason, Rock Island: Historical Indian Archaeology in the Northern Lake Michigan Basin (1986). Consider also Karl H. Schlesier, editor, Plains Indians, A.D. 500-1500: The Archeological Past of Historic Groups (1994), William H. MacLeish, The Day Before America (1994), and David Roberts, In Search of the Old Ones: Exploring the Anasazi World of the Southwest (1996). Perhaps a geologist or anthropologist colleague might be invited to offer some comments on pre-Columbian North America that will serve to illustrate, among other things, that history is related to other disciplines. Another suggestion is a lecture dealing with the Indian past prior to European arrival in the region in which the college or university is located using specialist resources specific to the area. For sources, consult the history of tribal groups that has been the concern of the University of Oklahoma's Civilization of the American Indian series, currently nearing two hundred volumes.