The US Open originated from two separate tournaments: the men's tournament and the women's tournament. The event was first held in August 1881 and staged at the Newport Casino, Newport, Rhode Island (men's singles only). The championships were known as the U.S. National Singles Championship for men. Only clubs that were members of the United States National Lawn Tennis Association were permitted to enter.
From 1884 until 1911 the tournament used a challenge system whereby the defending champion automatically qualified for the next year's final. The Newport Casino hosted the men's singles tournament until 1915 when it moved to the West Side Tennis Club at Forest Hills, New York. From 1921 until 1923 it was played at the Germantown Cricket Club in Philadelphia and returned to Forest Hills in 1924.
Six years after the men's nationals were held, the first official U.S. Women's National Singles Championship was held at the Philadelphia Cricket Club in 1887, followed by the U.S. Women's National Doubles Championship in 1889. The first U.S. Mixed Doubles Championship was held alongside the women's singles and doubles. In 1900, the U.S. National Men's Doubles Championship was held for the first time. Tournaments were held in the east and the west of the country to determine the best two teams (sectional winners). These then competed in a play-off — the winner played the defending champions in the challenge round.
The open era began in 1968 when all five events were merged into the newly named US Open at the West Side Tennis Club in Forest Hills, Queens. Notably, the 1968 combined tournament was opened to professionals; none of the predecessor tournaments allowed professionals to compete. That year, 96 men and 63 women entered the event with prize money amounting to $100,000. In 1970 the US Open was the first of the Grand Slam tournaments to introduce the tie-break at the end of a set.
The US Open was originally played on grass until Forest Hills switched to Har-Tru clay courts in 1975. In 1978, the event moved from Forest Hills to its current home at Flushing Meadows, and the surface changed again, to the current DecoTurf. (Jimmy Connors is the only man to have won the US Open on more than one surface; in fact, he won it on all three surfaces. Female player Chris Evert won it on two different surfaces.)