The US Open men's singles championship is an annual tennis tournament that is part of the US Open and was established in 1881. It is played on outdoor hard courts at the USTA Billie Jean King National Tennis Center in Flushing Meadows – Corona Park, New York City, United States. The US Open is played during a two-week period in late August and early September, and has been chronologically the last of the four Grand Slam tournaments of the tennis season since 1987. Newport (1881–1914), Forest Hills (1915–1920, 1924–1977), and Philadelphia (1921–1923) held the event before it settled in 1978 at the USTA National Tennis Center, now the USTA Billie Jean King National Tennis Center, in New York City. The inaugural tournament, in 1881, was reserved for United States National Lawn Tennis Association (USNLTA) club members, before the championships opened to international competitors in 1882. The USTA is the national body that organizes this event.