Observances featured honor guards, military band music, prayers and the laying of wreaths. A moment of silence was planned at 7:55 a.m. Hawaii time (12:55 EST).
A National Park Service event honoring veterans was planned at the World War II Memorial on the National Mall in Washington, Voice of America reported.
Hundreds of people were expected at the Pearl Harbor visitor center and memorial built over the sunken battleship USS Arizona.
In California's Contra Costa County, the Eye of Diablo, an 84-year-old beacon, was turned on -- it shines each year on Pearl Harbor Day.
On Dec. 7, 1941 -- a date President Franklin D. Roosevelt said "will live in infamy" -- Japanese aircraft attacked Pearl Harbor during the early morning hours.
More than 2,400 Americans were killed and five battleships were sunk in the attack, which drew the United States into World War II.