The 14 year old Ko shared medallist honours with 17 year old Korean Ji-hee Kim, the pair finishing at 6 under. Ko produced a second round of 66 to go with her opening 70 while the two shot first round leader, Kim, managed a 70 late in the day to join the world number one ranked amateur at the top of the leaderboard.
For Kim, despite her young age, this will be her last amateur event before turning professional and playing the Korean LPGA Tour. She was a member of the Korean Team which won last year's World Amateur Teams Championship.
In both of her strokeplay rounds, Ko has bogeyed her final hole but today she had reeled off four consecutive birdies from her 13th to 16th holes to at that point grab the outright lead. Kim was out nearly five hours after Ko and produced a solid round of 70 after an early bogey.
Elliott fought back from an opening 74 for a round of 70 and is in a share of 27th position while de Groot has consecutive rounds of 73 to be in a share of 45th.
For Elliott her performance was made even more meritorious by the fact that she has lost her luggage en route to Rhode Island as was forced to play with rented clubs in Monday's first round.
Thankfully for her the luggage arrived on Monday afternoon and with more familiar equipment was able to bounce back and comfortably force her way into the field for the remainder of the event.
In order for any of those through to the Match Play to become the US Women's Amateur Champion they will need to win six matches up to and including Sunday's 36 hole final.
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