2015 — Lydia Ko, 17, becomes the youngest golfer, male or female, to be ranked No. 1. She shares second place at the LPGA Tour’s season opener, where she finishes a shot behind Na Yeon Choi.

In 2012 Ko became the youngest player, male or female, to win a professional championship when she won the women’s New South Wales Open in Australia aged 14. A year later, at 15, she became the ...