The 6-3, 6-3 win at Flushing Meadows here on Sunday was the 18th Grand Slam victory for Williams. She is now tied with Chris Evert and Martina Navratilova for the fourth-most WTA titles in history, reports Xinhua.
"It means a lot to me," said Williams. "I just could never have imagined that I would be mentioned with Chris Evert or with Martina Navratilova, because I was just a kid with a dream and a racquet, living in Compton."
The ceremony was an emotional one. Williams tried hard to stop her tears.
"It's a pleasure for me to win No.18 here," Williams said. "I couldn't ask to do it at a better place."
Williams struggled to keep her first serve but followed with five straight breaks. With a 4-2 lead in hand, Williams went on to win the eight and tenth game to close the first set 6-3.
The second set saw Williams take a 2-0 lead again. The two players held serves until Williams broke Wozniacki in the ninth game to win the match.
Williams: It's a pleasure for me to win No.18 here
"None of the matches are easy," said Williams, who never needed more than two sets to win any match at the tournament. "Even today if I would have lost a game I would have been serving for it.
"Caroline was returning, starting to play a lot better, starting to return really, really well, and then she started serving really well. So we had longer points and we were running back and forth and back and forth. So it definitely wasn't anything that was easy."
Williams played an aggressive match. She had as many as 29 winners throughout the match, while Wozniacki only had four.
It was the second Grand Slam final for Wozniacki. The 24-year-old Dane reached the US Open final in 2009, but lost the match to Kim Clijsters. "When she's (Serena) on her game it's not fun to play her," said Wozniacki.
"She's so strong. She has a good serve and she puts pressure on you straightaway. Today, I went out there and I was a little nervous. I had a game plan in mind, but it was kind of difficult at the start. I tried to push her back, but that really didn't work for me. She really just stepped in and she was playing aggressive. She played better than me."