Johnson, a Welshman based in Arkansas, posted the first and only hole-in-one at the tournament when he drove the 301m par-four hole to perfection.
He chose his moment, getting the ace on the "party hole" in front of hundreds of revellers.
Johnson said he could not see the ball from the elevated tee and had to rely on the crowd's reaction.
"It's pretty cool down there," Johnson said. "It's a neat hole. I think every tournament should have one."
Johnson has had about seven holes-in-one in his career but only two on the Nationwide Tour.
His perfect shot yesterday earned him 1500 bottles of beer from sponsor Heineken.
He finished 11-under for the tournament, tied for 10th.
There were two aces at the 2007 Open at The Hills.
One, scored by Australian Steven Jeffress, was scored at the 15th.
