The history of the US Open started in 1968 when the 1st tournament took place at the West Side Tennis Club. That was when professional tennis players were allowed to take part in the Grand Slam tournament for the 1st time. Until then, only amateur players could compete in the previous US National Championships.
However, the 1st such tournament took place in August 1881 at the Newport Casino in Newport, Rhode Island and was played on grass courts. At that point, the tournament could only be attended by clubs that were members of the USNLTA (United States National Lawn Tennis Association).
Between 1921 and 1923, the tournament took place at the Germantown Cricket Club in Philadelphia and returned to the West Side Tennis Club in 1924 after the 14,000-seat Forest Hills Stadium was finished.
In the 1968 tournament, professional players were allowed to take part in all the events, except for the mixed doubles. A total of 96 men and 63 women entered the tournament, while the prize consisted of $100,000. The US Open became the 1st Grand Slam tournament that used a tiebreaker in order to decide a set that reached a 6–6 score in games, in 1970. It also became the 1st Grand Slam tournament that awarded equal prize money to both men and women, in 1973. The singles champions in that year were John Newcombe and Margaret Court. They received $25,000 each.
Since 1975, the tournament took place on clay courts instead of grass and matches could be played at night due to the floodlights.
The US Open moved to the USTA National Tennis Center in Flushing Meadows, Queens, in 1978 and its court surface went from clay to hard. At the same time, the tournament is the only one in the Grand Slam that has been played every year since it appeared. One of the most popular US open winners is Jimmy Connors, the only individual to have won the singles titles on 3 different surfaces (grass, clay, and hard). On the other hand, Chris Evert is the only woman to have some great US Open results, winning the singles titles on 2 surfaces (clay and hard).