Clarence Goodson started the scoring for the Americans in the 21st minute when he put Landon Donovan’s crossing pass in the back of the net.
Joe Corona made it 2-0 U.S. just eight minutes later when he blasted a shot into the left side of the net.
In the 39th minute El Salvador put some pressure on the Americans when Rodolfo Zelaya executed a penalty kick to make it 2-1.
The score stayed that way until the 60-minute mark when Eddie Johnson, who was substituted in 14 seconds earlier, scored on a header off a pass from Donovan.
Donovan then became the only player in history to score in six straight Gold Cups when he scored in the 78th minute.
The Americans have now won nine straight international matches as they advance to take on Honduras in the semifinals Wednesday in Dallas.
Copyright 2013 ABC News Radio
Madison Park, Keith Allen and Andreas Preuss, CNN