US Open (tennis)
The tournament was first played in 1881 for men, and 1887 for women. In 2006, the U.S. Open became the first Grand Slam to use Hawk-Eye. Hawk-Eye is a machine that can give a virtual replay of the shot that has just been played - this is useful for seeing if the ball was in or out. When a player does not agree with the umpire, they can ask to use Hawk-Eye. As of 2007, the other three Grand Slams use this machine too.