The double-decker bus rolled across the Bronx as a bespectacled guide in a crinkled jacket and tie pointed out notable attractions: Yankee Stadium, the Bronx Zoo and the Art Deco buildings along the Grand Concourse.

The guide, Lloyd Ultan, might have included himself as well.

Mr. Ultan, 77, born and raised in the Bronx, has served as the borough historian since 1996 and has become, to many, as synonymous with the Bronx as the landmarks and institutions that he knows by heart. A history professor at Fairleigh Dickinson University in New Jersey, Mr. Ultan has made a second career of documenting the borough’s often overlooked past. His vast knowledge of Bronx minutiae — shared with irrepressible, often corny humor — has earned him generations of fans.

“I’ve lived in the Bronx the whole time and I’m still here,” Mr. Ultan said. “I’m a stick-in-the-mud. Lord knows how much junk is rattling around in my brain.”

Now Mr. Ultan and Shelley Olson have written a book: “The Bronx: The Ultimate Guide to New York City’s Beautiful Borough” (Rutgers University Press). It covers major tourist attractions like the zoo and the New York Botanical Garden as well as lesser-known sites like the cottage that was Edgar Allan Poe’s last home and the Hall of Fame for Great Americans on the campus of Bronx Community College. It also includes walking tours of neighborhoods from City Island to Mott Haven.