Gibson announced last year that he had pancreatic cancer.
The legendary pitcher, who has played all 17 seasons of his career with the Cardinals, is a nine-time All-Star, Gold Glove and two-time World Series champion.
He was inducted into the Baseball Hall of Fame in 1981, his first year of eligibility.
Focused and determined as he was, he scored two contracts after college with both the Cardinals and the Harlem Globetrotters before deciding to stick with the former, second MLB.
In 1968, Gibson won his first Cy Young and MVP awards after finishing the season with 22 wins, a Major League record of 1.12 ERAs and 268 strikeouts. His dominant season in 1968 led MLB to lower the mound the following year.
Gibson retired after the 1975 season as the overall leader of the Cardinals for wins (251), strikeouts (3,117), shutouts (56), games started (482) and full games (255). Cy Young’s two-time winner holds the record for most strikeouts in a World Series match (17) and a World Series (35).
CNN’s Christina Maxouris contributed to this report.