On June 21, 1939, the New York Yankees announced Lou Gehrig's retirement after doctors revealed he had amyotrophic lateral sclerosis. From the article:
"Hall of Fame first baseman Lou Gehrig played for the New York Yankees in the 1920s and 1930s, setting the mark for consecutive games played. He died of ALS in 1941.
Who Was Lou Gehrig?
A standout football and baseball player, Lou Gehrig signed his first contract with the New York Yankees in April 1923. Over the next 15 years he led the team to six World Series titles and set the mark for most consecutive games played. He retired in 1939 after getting diagnosed with ALS. Gehrig passed away from the disease in 1941."