Richdale finished at 5-under-par 211, holding off four-time winner Vicky Hurst (72), who closed two shots back at 3-under-par 213. Jessica Shepley and Lisa Ferrero each carded final rounds of 1-over-par 73 to tie for third at 214 (-2).
Richdale was doused on the 18th green by fellow players who showered her with water bottles. Shortly after being escorted to the awards ceremony by generals from the reenactment soldiers of the Battle of Gettysburg, Richdale received the crystal cannon trophy from Pennsylvania native and LPGA and World Golf Hall of Fame member Betsy King. King served as the honorary chairperson at the Gettysburg Championship.
Richdale also received an Accutron diamond watch and moved from 50th to 17th on the season money list with a $14,000 paycheck.
'I'm really excited,' said Richdale, whose previous career-best finish was a tie for 17th at the Jalapeno Duramed FUTURES Golf Classic earlier this year. 'It's unbelievable. I wouldn't have told anyone that I could win one of the last few tournaments of the season.'
Richdale closed out her win with a birdie on the 18th hole, placing her 56-degree wedge approach shot eight feet away from the flagstick, then converting her birdie putt straight into the cup.
The Canadian had to overcome a pair of double bogeys after carding only two bogeys through her first 36 holes. Her second double-bogey on No. 13 dropped her back into a tie with Hurst at 4-under par. Her first double-bogey on the fifth hole gave Gerina Mendoza a one-stroke advantage.
'I got a little bit down on myself,' said Richdale after the double bogey on No. 5. 'I struggle in the bunkers as it is, and to get those two lies was really unfortunate. It was a tough pin placement and I just knew there were some birdies still out there.'
Richdale's first birdie of the day was a 25-footer on the par-3, sixth hole. She added back-to-back birdies on No. 10 and 11, from distances of eight and 10 feet, respectively.
Hurst had a chance to tie for the lead on the 18th green before Richdale's group came through, but the tour's top-ranked player missed a birdie putt as it trickled left of the hole.
'My game wasn't where I wanted it to be today,' Hurst said. 'I started very well, but after a bogey on No. 9, I couldn't really get that back.'