The stamps featuring boxing icon Muhammad Ali will debut on Thursday.
Ali was the first man to become a three-time heavyweight champion, but he also used his fame to advocate for peace and humanitarian issues.
In 2005, he was awarded the Presidential Medal of Freedom, which is the nation's highest civilian honor.
He died in 2016 at the age of 74 following a lengthy battle with Parkinson's disease.
The United States Postal Service also honored legendary martial artist and actor Bruce Lee.
A new forever stamp will feature Lee, who has inspired generations to explore the worlds of mixed martial arts, action movies, and Asian culture.
The stamp features Lee and his famous flying kick.
That stamp will debut in February.
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