Ken Burns is producing a four-hour PBS documentary on Muhammad Ali that is targeting a 2021 premiere.

The filmmaker said Wednesday has been working on the project since early 2016 with Sarah Burns and David McMahon. The same trio collaborated on 2013’s “The Central Park Five” and 2016’s “Jackie Robinson.” “Muhammad Ali” hails from Burns’ Florentine Films banner.

“Muhammad Ali may be the most iconic figure of the 20th century. He arrived at exactly the right moment, amidst the tumult and upheaval of the 1960s, and he shaped his times with his powerful voice, mesmerizing presence, and achievements in the ring,” said Ken Burns. “But beyond the astonishing athletic gifts and mountain of charisma, there’s a very complex, dynamic man whose life story has yet to receive the comprehensive treatment it deserves.”

The legendary boxer died last June at the age of 74. The scope of his influence makes him a ripe subject for the deep-dive treatment that is Burns’ hallmark. Sarah Burns noted that Ali was a divisive figure in his era with his early opposition to the Vietnam War and association with the Nation of Islam.

“We’re eager to get beyond the archetypes and examine who and what influenced his choices, and how he maintained the courage of his convictions when those choices seemed to go against the tide,” Sarah Burns said. McMahon added that there is no shortage of visual material available on the subject.

“Ali is among the most well-documented figures of the 20th century, filmed and photographed by the finest documentarians of his day. He was strikingly handsome, profoundly charismatic and knew how to draw a crowd and what to do once the cameras were rolling,” McMahon said.

Ken Burns’ latest work, “The Vietnam War,” is set to bow on PBS in September.