Mickey Mantle, 54, 1961
By 1961, the Mick already had a pair of MVP awards and 320 homers under his belt, having led the league four times, including a high of 52 in 1956 and 40 the year before. He jumped out to the league lead again with seven homers in 15 April games and still led after bashing another seven in May. But despite homering 11 times in June, he had been surpassed by hot-hitting teammate Roger Maris, who had homered just once in April but by the end of June led 27-25.
Aided by the league's addition of two expansion teams, the chase for Babe Ruth's single-season record was on, and the "M&M Boys" battled amicably, though Yankee fans had a clear preference for the homegrown Mantle. He trailed Maris, 40 to 39, by the end of July, a month that saw commissioner Ford Frick declare that Ruth's record would remain distinct unless surpassed within 154 games. Though still bashing at a prolific pace, Mantle trailed 56-53 through Sept. 10, but a right hip ailment and lingering cold, for which he received an injection—"amphetamines laced with vitamins, human placenta, and eel cells," according to biographer Jane Leavy—limited him to just one more homer the rest of the season; he developed an abscess that sidelined him for most of New York's World Series win over the Reds. Maris, of course, broke Ruth's record with 61.