Wambach scored on a penalty kick in stoppage time after Alex Morgan was fouled inside the area.
"It's not easy to score in international soccer, no matter who you're playing," Wambach said. "It's a pretty special night and I'm one more (goal) closer to getting (the record). ... I'm glad to have gotten the penalty kick. I think I deserved one earlier, but that's the way it goes."
Kristie Mewis opened the scoring in the third minute with her first international, and Lauren Cheney scored in the seventh minute. Cho Shoyun scored for South Korea in the 26th, and Carli Lloyd made it 3-1 with a 30-yard blast in the 57th minute.
The United States is unbeaten since March 2012, going 29-0-4, and is 8-0-2 on the year. South Korea is 3-4-1 this year. The teams will meet again Thursday night at Red Bull Arena in Harrison, N.J.
On the opening goal, Sydney Leroux raced toward the near post and fired a quick shot that goalkeeper Kim Jungmi got a piece of. But the rebound squirted to Mewis, who fired it into an open net.
"It was just amazing to be able to play in front of my family and friends," Mewis said. "Sydney made a great run down the end line and did all the work and I just kind of tapped it in."
Cheney doubled the U.S. lead 4 minutes later when she took Tobin Heath's pass and fired a shot inside the near post. South Korea countered on Cho's goal, with Ji Soyun crossing it toward the penalty arc for Cho, who blasted a shot past goalkeeper Nicole Barnhart.
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