Before the advent of the Open era of tennis competitions in April 1968, only amateurs were allowed to compete in established tournaments, including the four majors. There was no prize money and players were compensated for travel expenses only. However many top tennis players turned professional to play legally for prize money in the years before the open era. They played in separate professional events, mostly on tours involving head-to-head competition, but also in professional tournaments as the biggest events on the pro tour. Professional tournaments, in particular the professional majors, usually only had a men's draw. Professional majors In addition to the head-to-head tours, there were also major pro events, where the world's top professional male players often played. These tournaments held with a certain tradition and longevity. According to Ellsworth Vines, "the Wembley tournament in London..., the U.S. professional championship, and to some extent the tournament in Paris were the major professional tournaments prior to 1968." The oldest of these three tournaments was the U.S. Pro Tennis Championships, played at a variety of different venues and on a variety of different surfaces, between 1927 and 1999. The Wembley Championship, played between 1934 and 1990 at the Wembley Arena in the United Kingdom, was played on a wood surface through 1967. The third professional major was the French Pro Championship, where between 1930 and 1968 it was played on both clay and wood courts. A player who won all three in a calendar year was considered in retrospect by later tennis writers to achieve a "Professional Grand Slam", or "Pro Slam". In some years, professional tournaments other than the pro majors had stronger fields and offered more prize money. Jack Kramer designated the four major professional tournaments for the 1958/1959 seasons as follows; Forest Hills, Kooyong, L.A. Masters, Sydney. U.S. Pro Tennis Championships The U.S. Pro Tennis Championship, also known as the US Pro, and officially known as the Cleveland International Pro or Cleveland World Pro Tennis Championships between 1951 and 1962, was an annual tournament, later known as MFS Pro Championships. It was first organized by player Vincent Richards when promoter C. C. Pyle withdrew interest in the project. It was first played on the Notlek courts located at 119th Street and Riverside Drive, Manhattan. The tournament was held at various locations in several states until 1964, when it moved to the Longwood Cricket Club in Chestnut Hill,