Schultz led Robyn Puckett 3-up after 14, but Puckett won three straight holes to even the match. The duo matched pars on the 18th and 19th holes, before Schultz collected a third straight par to finish off the match.
'It's overwhelming,' Schultz exclaimed. 'I am so thrilled. I've wanted this for so long. This is what we work for and what we dream of. It's something everybody wants so badly.'
Puckett, who knocked off two-time defending champion Diane Lang on Wednesday, bogeyed the first two holes to drop 2-down.
Schultz quickly pushed her lead to 3-up with a birdie on No. 3. She stumbled to a bogey at four, but Puckett bogeyed the fifth to again fall 3-down.
Another Puckett bogey at the par-four ninth left her 4-down around the turn. The pair halved the next three holes before Puckett started her rally with a birdie on the par-three 13th.
Schultz faltered to bogeys on 14 and 16, while Puckett birdied the 15th. Puckett won those three holes to square the match.
'The mistake was 17,' Schultz stated. 'I didn't put a very good swing on the second shot. I should have bailed more left or taken the bunker out of play and then I got too greedy coming out of the bunker. That was the turning point.'
Schultz's par on the 20th hole gave her her first USGA title. She had previously lost this final last year and lost in the finals at the 2000 Women's Mid-Amateur.
'I was a little tired,' Puckett admitted. 'I don't play this much competitive golf. That's no excuse. I wasn't into it early on and I was trying to find myself. I was hacking away and all these nice people are out here and they want to see a good game. I just knuckled down.'