LONDON — Claressa Shields ducked one punch, deftly leaned away from another, and stuck her tongue out at her Russian opponent. Just an American teenager having a little fun.

After all, Nadezda Torlopova is nearly twice Shields' age and about half her speed. And Shields had to laugh at any boxer trying to get between her and a historic Olympic gold medal.

The 17-year-old middleweight from Flint, Mich., beat Torlopova 19-12 on Thursday, capping her rapid ascent through women's boxing with a title in its Olympic debut.

"This was something I wanted for a long time, even when boxing wasn't going all right, even when my life wasn't going all right," said Shields, who found sanctuary in a boxing gym during a rough childhood.

"All I wanted was a gold medal, and I kept working towards it, even when people were saying I couldn't do it. I'm too young. I couldn't do it. There were girls who were going to beat me because of better experience, more experience. I proved them all wrong."

Shields did it in style — shuffle-stepping, brawling and even winning over a crowd that showed up to cheer Irish lightweight Katie Taylor and British flyweight Nicola Adams, who also won gold medals.

Shields won the 12-member American team's only gold medal in London as the winningest nation in Olympic boxing history got no medals from its men's team for the first time.