This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The tournament now called the US Open began as a men only event in August 1881, organized by the newly formed United States National Lawn Tennis Association at the Newport Casino in Rhode Island. A separate women's national championship followed in 1887, six years later, first held at the Philadelphia Cricket Club rather than at Newport, and the men's and women's championships were not merged into one combined event at a single site until 1968.
That 1968 merger arrived alongside the tournament's larger transformation: the start of the Open Era, when for the first time professional players were permitted to enter alongside amateurs, ending a distinction that had shaped the tournament, like the sport generally, since 1881. The championship adopted its now familiar name, the US Open, that same year, retiring the US National Championships title the event had carried for eighty seven years.
Billie Jean King's 1973 campaign for equal prize money made the US Open the first of the four majors to pay its men's and women's singles champions the same amount, a change other majors did not match for decades afterward; Wimbledon was the last of the four to equalize prize money, in 2007. The tournament's move to hard courts, and its reputation for late night finishes under the lights of a major media market, have given the US Open a character distinct from the other three majors' older, more tradition bound settings, even though its own origin in 1881 makes it, after Wimbledon, the second oldest of the four.