In 1968, McLain became the last pitcher in Major League Baseball to win 30 or more games during a season (31–6) — a feat accomplished by only 11 players in the 20th century.

McLain was brash and outspoken, sometimes creating controversy by criticizing teammates and fans with little provocation. His stellar performance at the beginning of his major league career included two Cy Young awards and an American League MVP award. His success in baseball stood in marked contrast to his personal life, where he associated with organized crime and was eventually convicted on charges of embezzlement, after which he served time in prison.

This Rawlings official MLB baseball was signed in blue ballpoint pen by McLain and inscribed, "31-6, 1968." This ball includes a Tri-Star hologram and COA.