July 4th was the last star to be added to our flag! (Independence day) And the year was 1960
It was added in 1960 on 4th of July, around year after Hawaii joined the union (exact date of joining is August 21, 1959).
The last star added to the American flag was in 1960 for Hawaii as the 50th state. The new flag design was officially adopted on July 4, 1960. This addition completed the current design of the flag that symbolizes all 50 states.
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