Vollmer beat out China's Lu Yinh and Austrailia's Alicia Coutts, herself a gold medalist for the 4x100-meter relay, to score the gold.
Vollmer managed to score the win and the gold record even after losing her swim cap halfway through the race.
"The top cap came off," Vollmer told NBC. "I have never had that happen before. I thought about it, and maybe it kept my mind off my legs hurting or something. I don't know. It's just so exciting, the whole thing."
Vollmer, 24, previously performed in the 2004 Olympics at age 16, swimming in a relay. While Vollmer was expected to perform at the 2008 Beijing Olympics, a mystery illness kept her off the team. She was later diagnosed with an allergy to eggs, and after switching to a new, gluten-free diet, Vollmer easily won qualifying rounds for the these Olympics in Shanghai.
After Ryan Lochte's impressive performance in the 400-meter individual medley won the U.S. its first gold medal on Saturday, Vollmer has carried on the tradition of a strong U.S. swim team.