Olivia Culpo, a 20-year-old sophomore at Boston University, took the title during Wednesday night's pageant.
An American had not won the pageant since Brook Lee took the crown in 1997, according to the Associated Press.
Culpo beat out 88 other contestants during the competition, held at the Planet Hollywood casino in Las Vegas.
Miss Philippines Janine Tugonon was the runner-up, while Miss Venezuela Irene Sofia Esser Quintero came in third.
In June, Culpo became the first Miss USA winner from Rhode Island. Her parents are both professional musicians, and Culpo has played the cello alongside world-renowned classical musician Yo-Yo Ma.
Miss Maryland Nana Meriwether now becomes the new Miss USA. Leila Lopes of Angola is the outgoing Miss Universe.