Martin Luther King Jr. is shot dead at the Lorraine Motel in Memphis, Tennessee, triggering riots in many American cities.
North Vietnamese forces besiege the US Marine base at Khe Sanh in Quảng Trị; US forces abandon the base in July.
North Vietnamese and Viet Cong forces attack more than 100 cities and towns in the South; despite heavy losses, the offensive erodes US public support for the war.
US soldiers of Charlie Company kill hundreds of unarmed civilians at Sơn Mỹ, Quảng Ngãi; the killings become public in 1969.
Neil Armstrong and Buzz Aldrin become the first humans to walk on the Moon.
The first message is sent between UCLA and the Stanford Research Institute over ARPANET, the precursor of the Internet.
A sustained US aerial bombing campaign against North Vietnam.