Kangs putt capped off a 3-under round of 68 for a 36-hole total of 4-under 138 on the 6,422-yard, par-71 layout at Old Warson Country Club. The 16-year-old Kang edged Marina Alex, 19, of Wayne, N.J., and 16-year-old Jessica Korda of Bradenton, Fla.
Alex and Korda, both finished at 3-under 139.
Kang, competing in her second Womens Amateur and sixth USGA championship, registered seven birdies and four bogeys. The round included three consecutive birdies from No. 12.
Im excited, Kang said. My dad was like, Lets get medalist today. I wanted to accomplish something for making match play.
Kordas 4-under-par 67 tied for the lowest round of the championship with 17-year-old Sun Gyoung Park of Vail, Ariz., who finished fourth at 140 after a 67 on Tuesday.
First-round leader Amy Anderson, 17, of Oxbow, N.D., had a 75 and finished at 1-over 143. The newly minted U.S. Girls Junior champion was bidding to become the third player in USGA history to earn medalist honors in the Girls Junior and Womens Amateur in the same year.
The incoming North Dakota State freshman still has a chance to become the first player to win both titles in the same year.
The match-play cut was at 9-over 151, with six golfers playing off for the final spot. Amelia Lewis, 18, of Jacksonville, Fla., was the survivor.
Sixty-four golfers will begin match play on Wednesday morning, leading up to the 36-hole final on Sunday.