On May 4, 1966, Willie Mays of the San Francisco Giants establishes a new National League record for most career home runs. The âSay Hey Kidâ hits his 512th home run, surpassing the total of former New York Giants great Mel Ott. Maysâ blast against Claude Osteen, which puts him fourth on the all-time list, helps the Giants beat the Los Angeles Dodgers, 6-1.