Known as "The Greatest," Muhammad (1942–2016) was a three-time heavyweight boxing champion. In his life, he challenged the best fighters in the world - and the world itself. At a time when African Americans fought to have a voice, Ali spoke loud and clear about his beliefs, defying expectations and empowering people around the world on his way to becoming a globally celebrated cultural icon.

Designed in a checkerboard configuration on the pane, the stamps feature a black-and-white Associated Press photograph of Ali from 1974. "His good looks are apparent, and the direct eye contact is compelling" says USPS Art Director Antonio Alcalá, explaining why he chose the photo. "The stance and boxing gloves clearly communicate how he became an American sports icon."

On the stamps, the name "ALI" alternating top to bottom, dark brown to red, suggests aspects of his boxing career: the capital letters of promotional posters, his legendary movement in the ring, and the chants of "Ali! Ali! Ali! Ali!" that greeted him when he traveled the world.

"The greater the fame of the individual, the more people have an opinion of the 'right' way to represent that individual on a stamp,” notes Alcalá. "Ali, in his heyday, was arguably the most famous person on the planet. So, designing a stamp that would resonate with everyone was a challenging task."

The selvage shows a black-and-white 1976 Associated Press photo of Ali in a pinstripe suit, a recognition of his wider cultural importance as an activist and humanitarian.

"There are many facets to Ali," Alcalá says. "I felt it was important to represent him on the stamp as a boxer, but also to include a photo showing his non-boxing side."