Steve Allen began hosting "The Tonight Show" in 1954 at the age of 32, making him the youngest host in the show's 70-year history. Jack Paar, the next permanent host, took over in 1957 at 39—the same age Jimmy Fallon was when he assumed the role in 2014. Johnny Carson, the show's longest-serving host, began his tenure in 1962 at 36, later passing the torch to Jay Leno, who was 42. Surprisingly, Conan O'Brien holds the record as the oldest initial host, starting at 46. (Although Jay Leno was older when he resumed hosting duties from Conan.)
