What Year were Professional Tennis Players fully admitted to compete in all Four Majors?

The four grand slam events where also established in this era, with Wimbledon in 1877, the U.S. Open four years later, the French Open (1891) and Australian Open in 1905.

The U.S. Professional Championship was first held in 1927, but it was not until 1968 that the four grand slams allowed professionals to play, beginning the modern "Open" era.