After Ditko's left Marvel in 1966, John Romita Sr. became Lee's collaborator on "The Amazing Spider-Man". Within a year, it overtook "Fantastic Four" to become the company's top seller. Lee and Romita's stories focused as much on the social and college lives of the characters as they did on Spider-Man's adventures. The stories talked about issues at the time such as the Vietnam War, political elections, and student activism. Lee created the Black Panther, an African king who would be mainstream comics' first black superhero.