(CNN) For anyone who doubted her, it's official: US Olympic gymnast Simone Biles is #1.

The 19-year-old powerhouse proved her dominance in the sport on Tuesday with a practically flawless floor routine that won her a fourth gold medal in Rio.

Teammate Aly Raisman, the reigning Olympic champion on the floor, took second place with a score of 15.500, making it the second 1-2 win for the two American gymnasts this Olympics.

Biles scored a 15.966 in the floor exercise final with a series of difficult moves executed to near-perfection, including the signature move named for her.

The Biles is a double layout with a half-twist and a blind landing. She performed the move, ending it with a stag leap that she had left out of her team performance but added back for the individual all-around.