The US Open, formally the United States Open Tennis Championships, is a hardcourt tennis tournament which is the modern iteration of one of the oldest tennis championships in the world, the U.S. National Championship, which for men's singles was first contested in 1881. Since 1987, the US Open has been chronologically the fourth and final tennis major comprising the Grand Slam each year; the other three are the Australian Open, French Open and Wimbledon.
It is held annually in August and September over a two-week period (the weeks before and after Labor Day weekend). The main tournament consists of five different event championships: men's and women's singles, men's and women's doubles, and mixed doubles, with additional tournaments for senior, junior, and wheelchair players. Since 1978, the tournament has been played on acrylic hard courts at the USTA Billie Jean King National Tennis Center at Flushing Meadows-Corona Park in Queens, New York City.
The US Open has tiebreaks in every set, including the last set. The other three Grand Slam tournaments have tiebreaks in every set other than the last set (i.e. the fifth set for men and third set for women), and therefore their last set continues indefinitely until a two-game lead is reached.