The Stoke-based golfer finished behind winner Rory McIlroy on five under and as a result receives an automatic berth in next year's Masters.
Lynn's previous best finish in a major came in the 2003 Open where he came in at tied for 53rd and the 38-year-old is ecstatic after his performance in the USA.
"To get in is just a dream come true, obviously - amazing," he said.
"I saw Rory at 11 [under] and I thought he's not going to mess up from there. It was just a case of playing for as good a position as I could.
"I've never been exempt to play in anything in America before, so that's the reason why I've never been over here. This is a good start."
Lynn qualified for the US PGA Championship after breaking into the world top 100.