Bobby Jones
An amateur who defeated the world’s best professionals, Jones swept the British and U.S. Opens and Amateurs in 1930. He retired from competition at 28 and later helped found Augusta National.
Jones's 1930 sweep belonged to a different championship structure: the U.S. Open, The Open, the U.S. Amateur and the Amateur Championship. A modern four-major comparison misses how difficult it was for one amateur to win all four in the same season.
His victory at Merion completed the feat and closed his competitive career. He later helped create Augusta National and the Masters, so his influence continued long after his last tournament shot.
Jones's place reflects the period in which amateur golf carried enormous prestige. His Grand Slam was a sweep of the four championships that mattered most to his era, achieved while working as a lawyer.