Here is how close the difference was between gold and silver:
Adrian: 47.52 seconds.
Magnussen: 47.53 seconds.
It was a personal-best time for Adrian, who graduated from Bremerton High School in 2006 and went on to attend University of California-Berkeley.
Brent Hayden of Canada took third in 47.80 and defending Olympic champion Cesar Cielo of Brazil was well back in sixth place.
Cielo, in fact, was the only non-American to win this event in the last three Games.