Shane Lowry, who led after each to the first two rounds and was in or near the lead all the way, closed with a 70 to finish two shots back in a tie for third with Patrick Cantlay of Los Alamitos and UCLA, and Scott Piercy, who both totaled 69.
Johnson, a SC native, shot a three-under 68 in trying conditions to end on 10-under 203, making his move with three consecutive birdies from the 13th and holding on to his lead despite dropping shots at 16 and 17.
He's exempt on tour through 2020-21, in line to make the President's Cup International team this year and will have an opportunity he's dreamed about since taking up the game in the mid-1990s by playing at Augusta National.
Pan's breakthrough came in his 79th tour event after only seven prior top-10 finishes.
"Yeah, so this week I'm having my first AJGA events in Houston", said Pan.
The 27-year-old Pan - who turned professional in 2015 - finished 12 under on the Harbour Town Golf Links, holding a one-shot lead with golfers still on the course.
Cheng-Tsung Pan of Chinese Taipei plays his shot on the fourth hole during the second round of the 2017 U.S. Open at Erin Hills on June 16, 2017 in Hartford, Wisconsin.
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"When I was younger it was just a goal to be on the LPGA Tour, to win my first event, " Henderson said. The 53-year-old McCarron finished at 7-under 209 for his ninth victory on the 50-and-over tour.
Listen to your wife was the clear message that came from C.T. Pan as he claimed his maiden PGA Tour title at the RBC Heritage on Sunday: Without her influence, he might not have even played.
But that all changed in a matter of minutes starting on the 11th hole of the final round; A 436 yard dogleg right. He denied Robby Shelton a victory in his home state. Pan follows in the footsteps of Satoshi Kodaira from Japan, who won last year's event. Johnson entered the final round at 10 under, but he shot a 6-over round of 77 and finished tied for 28th. Shelton closed with a 69 to join him at 15-under 273.
They traded pars twice on the 18th hole and once on the ninth hole during the playoff before Griffin hit his approach on the 18th to 3 feet.
LPGA - Brooke Henderson successfully defended her title in the Lotte Championship in Kapolea, Hawaii, to tie Sandra Post's record for LPGA Tour victories by a Canadian with eight.
George Knudson and Mike Weir share the Canadian mark on the PGA Tour, also each winning eight times. Ariya Jutanugarn (73) and Minjee Lee (74) tied for third at 11 under.