List, who is looking to win on the U.S. PGA Tour for the first time, carded five birdies, including one on the par-5 9th, his final hole, to move to 9 under.
"Some positive vibes there," List said. "Anytime you get a bogey-free you are really happy about it. The wind was tricky but I was able to save par a lot and play solid in the back nine."
Three-time tour winner Lucas Glover compensated for a pair of bogeys with seven birdies in a 67 and was tied for second with Scott Brown, who had a 70.
A day after firing a 63 for the first-round lead, Justin Thomas made a 74 to slip into a share of fourth with Australian golfer Cameron Smith (68) at 7 under.
Thomas took a three-shot lead into the second round, but an opening 3-over-par 39 on the front brought him back to the pack.
The second-round 74 is Thomas' worst score since an 80 in the second round of the British Open.
Jason Day also struggled en route to a 74 to fall back to 24th at 2 under.
Whee Kim (70) was the highest placed of the 16 South Korean players in the field at 6 under overall, tied for sixth with Patrick Reed (72), Chez Reavie (72) and another Australian, Marc Leishman (72).
Seung Yul Noh carded five birdies and closed with an eagle in a bogey-free 65 for the best score of the day, lifting him to even par overall.
Conditions so far have been windy and List said he expects that to be a factor on the weekend.
"If the wind does not blow out here, there will be a lot of birdies," List said. "If the wind does blow, you can kind of be a little bit more strategic and try to make some pars out there."
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