When was the first tennis major comprising the Grand Slam before the US Open first held?
US Open (tennis) The United States Open Tennis Championships is a hard court tennis tournament. The tournament is the modern version of one of the oldest tennis championships in the world, the U.S. National Championship, for which 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, in chronological order, are the Australian Open, the French Open and Wimbledon.
1990 ATP Tour The 1990 IBM ATP Tour was the first season of the ATP Tour, the newly formed tennis circuit which came in to replace the Grand Prix and WCT tournaments. It was the elite tour for professional tennis organized by the Association of Tennis Professionals. In 1990 the IBM ATP Tour included the four Grand Slam tournaments, the ATP Tour World Championships, the ATP Championship Series, Single-Week, the ATP Championship Series and the ATP World Series. The World Team Cup and Davis Cup are included in this calendar but did not count towards the Tour.