Pearl Harbor was a US Naval base in WW1. But its place in History is in WW2 when the Japanese launch a pre emptive air strike from carrier based aircraft. This is known, Dec 7th 1941, as the day that will live in Infamy.
The Japanese attacked Pearl Harbor and a number of other targets on Hawaii and other Pacific locations on December 7, 1941. Then President Franklin Roosevelt called it "A date which will live in infamy."