The 59-year-old Elliott, from West Des Moines, Iowa, wins for the first time in 36 starts in USGA events. He also won the Senior British Amateur at the Ganton Golf Club in England this summer.
The 58-year-old Gunthorpe, from Ovid, Michigan, never dragged until he missed an 8-foot putt at 18.
“The match was so hard I’m not sure, did I win?” Elliott said. “I think it’s not sunk in yet. Just as much goes with the USGA title that maybe that’s why I have not won it in the past. It’s just as important and so significant to win a USGA championship. “I’m I’m very proud. I did not do it myself. I got a lot of help from a lot of different people, so it’s a team victory.”