Webb Simpson, another North Carolinian who was bidding to win the Wyndham for the second time (2011), birdied the 18th hole to shoot 65 and finish second, a shot back.

“Congrats to J.T., he played phenomenally today,” Simpson said. “Happy for him. He’s a young player, such a nice kid, so I’m happy for him.”

Simpson wasn’t the only one; this was, to put it mildly, a popular victory. In addition to his grandparents, Poston’s mother, Cheryl, and father, Ty, were here. His brother, Bailey. His coach, John McNeely, who gave him a lesson on his takeaway just days before the tournament started that proved to be hugely helpful. Cousins. Friends.

Also over the moon were fellow players Patton Kizzire, who waited behind the green for Poston to roll in the testy 4-footer for par on 18, and Denny McCarthy, who didn’t quite get back in time.

“I’m in the middle of a laundry cycle at the hotel,” McCarthy said with a laugh. “And I just left my clothes in the wash right now. I wouldn’t miss this. He’s been a great friend to me the last couple years and he deserves this so much. He’s always shot me a text when I have success, or when I’m down.”

Keith Mitchell, who won The Honda Classic earlier this season and lives with Poston as roomies at a house in St. Simons Island, Georgia, was trying to steady his breathing in front of the TV at home. Poston was there waiting for Mitchell when he won The Honda, and Mitchell so badly wanted to return the favor he said he tried to rent a plane to get to Greensboro in time to watch the back nine. Alas, he was told the weather was too poor.

“We tried everything we could,” Mitchell texted.

Poston attended Western Carolina in tiny Cullowhee, about three and a half hours away, and his mother reported seeing copious Catamounts purple at Sedgefield.

“It’s amazing how many people were out here pulling for him,” said McNeely, his coach.

No one, though, had quite as personal a stake as Poston’s grandfather.

Cunningham, who played in two U.S. Senior Amateurs and two British Senior Amateurs, used to drive Poston and his friends to junior tournaments, and before that he cut down a persimmon 5-wood, pried off the sole, and took the weight out to create the kid’s first club. Poston was 3.

“I can remember as a kid following him to the range, and taking that 5-wood and just hitting balls for hours and loving every minute of it,” said Poston, who moved to 27th in the FedExCup and qualified for the Masters Tournament and Sentry Tournament of Champions, among other elite events. “I mean, our relationship, a lot of it has revolved around golf. … I learned from him, just from watching him and how he carried himself, when I was a kid.”

Cunningham has had some health problems and been unable to attend many tournaments, but he walked the front nine Sunday before going in for some lunch. He came back out and did six holes of the back nine. He said Poston was 12 or 13 when he beat his grandfather for the first time.

“I think he shot 76 and I shot 77,” Cunningham said. “It wasn’t an easy course. I’ve still got that scorecard.”

The sand castle will not last. The rains will come, even if they mercifully held off for 72 holes, and his name will dissolve into slurry. But it will be on a plaque on the Wall of Champions behind the ninth green. That will endure, and so will the memory of winning in front of the man who started it all, the man he calls Pa Doc.

“For him to be here,” Poston said, “that’s something that I will never, never forget.”