Gibson announced last year that he had pancreatic cancer.
The legendary pitcher, who played all 17 seasons of his career with the Cardinals, was a nine-time All-Star, Golden Glove winner and two-time World Series champion.
He was inducted into the Baseball Hall of Fame in 1981, his first year of eligibility.
Gibson was born in Nebraska in November 1935 and was the youngest of seven children, according to the Major League Baseball website.
As a child, he overcame episodes of asthma, rickets and heart murmurs, but still became Creighton University’s first African-American baseball player and basketball player, according to MLB.
Focused and determined as he was, he signed two post-college contracts with the Cardinals and Harlem Globetrotters before ultimately deciding to stick with the former, according to MLB.
In 1968, Gibson won his first Cy Young and MVP awards after finishing the season with 22 wins, a major league record 1.12 ERA and 268 strikeouts. Its dominant season in 1968 led the MLB to lower the mound the following year.
Gibson retired after the 1975 season as the Cardinals’ all-time leader in wins (251), strikeouts (3,117), shutouts (56), games started (482) and games played. complete (255). Two-time winner Cy Young holds the record for most strikeouts in a World Series game (17) and a World Series (35).
“I was just over there doing what I knew how to do and it’s about as easy as it gets,” Gibson said in a previous interview posted in an MLB video this week.
Gibson’s death comes just weeks after the death of two other baseball legends: Hall of Famers Tom Seaver and Lou Brock.
CNN’s Christina Maxouris contributed to this report.