Bill Madlock was born in Memphis, Tennessee, but grew up in Decatur, Illinois, where he graduated from Eisenhower High School.

[3] He accepted one of the two baseball scholarships, at Southeastern Community College in Keokuk, Iowa, because of his preference for playing a less hazardous game.

His reasoning was clear from what he later told a Sports Illustrated reporter: "I didn't want to have 6'5", 250-pound guys bearing down on me, so I decided to play baseball.

By the time Madlock was ready to sign with a major league baseball team, he had decided to go with an offer from the Washington Senators organization.

Prior to his promotion, he led the Pacific Coast League in total bases (268) and runs scored (119), finished second in batting (.338) and had 22 homers and 90 RBI at Triple-A Spokane.

His new manager with the Cubs Whitey Lockman said about him, "Our scouts are extremely high on Madlock as being one of the best hitting prospects they have seen in some time.

In 1976 Madlock repeated as batting champion with a .339 average, edging out Ken Griffey Sr. of the Cincinnati Reds on the final day of the regular season (October 3, 1976).

Griffey belatedly entered his team's game (which the Reds won 11–1 over the Atlanta Braves), and went 0-for-2, dropping his average to .336.

"[7] In what was considered one of the five worst trades in Cubs history by the Chicago Tribune's Chris Kuc in 2016,[8] Madlock and Rob Sperring were dealt to the San Francisco Giants for Bobby Murcer, Steve Ontiveros and minor-league right-handed pitcher Andy Muhlstock on February 11, 1977.

In 1980 Madlock's average dropped to .277 as the Pirates finished third in the National League East, eight games behind the eventual World Champion Philadelphia Phillies.

Madlock poked umpire Jerry Crawford in the face with his glove after being called out on strikes with the bases loaded.