Arthur Ashe Stadium started to fill up as the semifinals of the women's singles event got underway.
Maria Sharapova came out strong against Victoria Azarenka in the first semifinal, taking the first set.
But Victoria Azarenka would find her range in a 6-2 second set and push the semifinal to a third.
The two held for the first nine games of the third but the 10th game was trouble for Maria Sharapova.
Victoria Azarenka snatched the first break of the third set in the final game to prevail, 36 62 64.
Victoria Azarenka moved into her second Grand Slam final, having won the Aussie Open earlier this year.
Victoria Azarenka had never even been to the quarters of the US Open coming into this year's event.
Eva Longoria and Venus Williams were among those in Serena Williams' player box in the next semifinal.
Sara Errani had followed up her French Open final with another Grand Slam semifinal in the Big Apple.
Serena Williams blasted 38 winners during the match, off every shot - serve, forehand, backhand...
Serena Williams met Sara Errani at the net after a 61 62 win. She has won 42 of her last 44 matches.
You win, you always do - Will Ferrell was in the crowd for Victoria Azarenka and Serena Williams' wins.
A day earlier the mixed doubles final took place, with Ekaterina Makarova winning her first major.
Ekaterina Makarova partnered Bruno Soares to defeat Kveta Peschke and Marcin Matkowski in the final.
The winning pair actually saved two match points to win the final in a match tie-break, 67(8) 61 1210.