Ernie Banks signed with the Kansas City Monarchs of the Negro American League in 1950 and broke into the major leagues in 1953 with the Chicago Cubs as their first black player. He played for the Cubs his entire career, starting at shortstop and moving to first base in 1962. Banks wore number 14 as a Cub, and is one of only four Cubs players who have had their number retired by the organization. He is well known for his catch phrase of, "It's a beautiful day for a ballgame... Let's play two!", expressing his wish to play a double-header every day out of his pure love for the game of baseball, especially in his self-described "beautiful confines of Wrigley Field". In 1955, he set the record for grand slams in a single season, at an amazing 5. (This record stood for over twenty years.)

Banks won the National League Most Valuable Player Award twice, in 1958 and 1959. This feat is amazing, since the Cubs were never pennant contenders during Banks' career and this award is usually given to players who contribute substantially to their teams' championship drives.

Despite never having appeared in a postseason game, Banks is regarded as the most popular baseball player in Chicago history, leading to his nickname of "Mr. Cub." On August 22, 1982, his uniform number 14 became the first to be retired by the Cubs. It had already been de facto retired for nearly 9 years, not having been assigned to anyone else following Banks' retirement from the coaching ranks.

In 1977, in his first year of eligibility, Banks was elected to the Baseball Hall of Fame.

In 1999, he ranked Number 38 on The Sporting News list of Baseball's Greatest Players, and was elected to the Major League Baseball All-Century Team.