Joaquin Niemann carded an eight-under 62 to move into a three-way tie for the Greenbrier Classic lead, but the second round belonged to Kevin Chappell.
Niemann, 20, sits at 13 under alongside Scottie Scheffler (62) and Robby Shelton (65) at the halfway mark of the opening event of the 2019-20 PGA Tour season.
But it was Chappell who stole the show, the American becoming the 11th man in PGA Tour history to card a sub-60 round, shooting an 11-under 59.
Chappell marked his first PGA Tour start since November 2018 following microdiscectomy surgery on his back by entering the record books in West Virginia.
He followed up his opening-round 71 with the bogey-free 59, which featured eight consecutive birdies from holes 11 through 18.
The spectacular round was enough to see Chappell sit in outright fifth at 10 under, behind the leading trio and Adam Long, who is at 12 under.
While not as impressive as Chappell, Niemann – a former top-ranked amateur – holed six birdies and an eagle during his round.
Scheffler and Shelton, meanwhile, continued their consistent starts to share a one-stroke lead over Long.
A group of six – Sam Ryder (66), Cameron Smith (64), Morgan Hoffmann (65), Harris English (65), Harold Varner III (66) and Brian Harman (66) – are tied for sixth at nine under.
Defending champion Kevin Na is back in a tie for 25th after following his opening-round 64 with an even-par 70.
Scott Stallings, the 2011 champion, was among the players to miss the cut.