When Alan Shane Dillingham, a historian at Spring Hill College in Alabama, lectures on the 1960s he starts by displaying a timeline of the decade’s most iconic, tumultuous year — 1968.

The assassinations of the Rev. Martin Luther King Jr. and Robert F. Kennedy. The riots that shook Washington, Chicago, Baltimore and other U.S. cities. Campus protests. Civil rights protests. Vietnam War protests. The Tet Offensive. The My Lai massacre. The rise of Richard Nixon and the retreat of Lyndon Johnson. And so much else: Black Power, “The White Album,” Andy Warhol, “Hair,” Apollo 8, the first black character in Peanuts.

“Was there something in the water?” Dillingham asks his students. “What is it about this year?”