[2016-05-18 12:00:00] With school nearly out, many families are gearing up to take the great American road trip. This hour, we’ll talk about must-visit stops along the way with Brent D. Glass, director emeritus of the National Museum of American History. His new book is called “50 Great American Places: Essential Historic Sites Across the U.S.” (Simon & Schuster), and he’s in town to talk about it tonight at the Sixth Floor Museum.