Prior to the meeting in Italy, the American had just two World Cup wins to his name, with both coming at this venue, in 2006 and 2012.
And Nyman completed a treble of successes on Friday by finishing ahead of the in-form Kjetil Jansrud.
Nyman clocked a winning time of one minute 55.89 seconds, which was 0.31secs quicker than that of Jansrud.
The Norwegian, who won gold in the super G and bronze in the downhill at the 2014 Winter Olympic Games, had tasted victory in both of the first two downhill meetings of the season.
And he continued his fine form with second place here, taking his lead at the top of the downhill standings to 105 points.
Nyman's triumph sees him move to second, and the American hopes his success can act as the springboard for further glory.
"I really hope I can carry it throughout the season and push for a title," he said.
"Jansrud's in such good shape, so I've got a lot of work ahead of me."
Nyman is just ahead of Guillermo Fayed in the standings, after the Frenchman finished fourth on Friday.
Home favourite Dominik Paris achieved a third-place finish, although he was over a second behind the leading time of Nyman.
Olympic champion Matthias Mayer finished seventh, 1.53secs behind the winner while Christof Innerhofer, who claimed silver in Sochi, was way down in 23rd.