List of Grand Slam men's singles champions
Many changes in the Grand Slam tennis tournaments have affected the number of titles won by various players during its history. These changes have included the opening of the French national championships to international players in 1925, the elimination of the challenge round in 1922, and the admission of professional players in 1968 (the start of the Open Era).
Source: Wikipedia — List of Grand Slam men's singles champions (CC BY-SA 4.0)