Young made two eagles and seven birdies at the TPC River Highlands course for the first sub-60 score in nearly four years on the PGA Tour.
Yang, 34, has carded just three bogeys in 54 holes as she looks to add a major title to her five LPGA Tour wins.
The world number one said there ‘no words’ for how she is playing as Sarah Schmelzel and Amy Yang claimed the halfway lead.