The two quickest times in history were recorded in a thrilling showdown between the Soviet Union and the USA at the 1988 Seoul Olympics.
The USA took a narrow first-leg advantage with Denean Howard (49.82). However, the Soviets stormed back on leg two with Olga Nazarova (47.82). But then the USA hit back on leg three with Valerie Brisco (48.44).
The anchor leg was a mouthwatering battle: Olympic 400m champion Olga Bryzgina (47.80) held off Florence Griffith Joyner (48.08), who had stormed to gold in the 100m, 200m and 4x100m relay.
The Soviet quartet posted a world record of 3:15.17.