His last was of 67, sealing a three-shot success.
He had treatment over the weekend but said after his three-shot success: "It was perfect.
Last month's Players Championship success by Kaymer was bettered by his eight-shot success at the US Open on Sunday.
Married as a teenager, he and his wife, Crystal, have three young children and, in all likelihood, a narrow window to maximize Rahman's one-shot success.
He had a final round of 70 for a 22-under-par aggregate, ensuring a three-shot success over Alex Noren.
It was a fine reminder of what got them to this round and a good barometer of whether that audition was a one-shot success or demonstrated real potential.
Jordan Spieth immediately set his sights on retaining the Masters, after becoming the second youngest winner in the event's history with a four-shot success at Augusta National on Sunday.
According to the Austin, Texas-based company TrackingPoint, the addition of its scope to a rifle delivers five times the first-shot success rate of traditional systems at distances of up to 1,200 yards (1.1km).
Rory McIlroy, McDowell's successor as US Open champion, plays with defending champion Hunter Mahan in his first start in America since his eight-shot success in Washington in June.
