Margaret Court was the first woman to win the Grand Slam in a single calendar year during the Open Era.
The Australian won all four major singles tournaments in 1970: the Australian Open, French Open, Wimbledon, and US Open. Winning each major in the same calendar year is known as a calendar-year Grand Slam. Court completed the sweep at the US Open, defeating Rosemary Casals in the final.
The Open Era began in 1968, when professional players were allowed to compete alongside amateurs in major tournaments. Court’s achievement therefore came after that turning point, although Maureen Connolly had completed a calendar-year Grand Slam in 1953, before the Open Era.
Court’s 1970 season is sometimes mixed up with Steffi Graf’s 1988 Grand Slam. Graf also won all four majors in one year and added Olympic gold, creating what is called the Golden Slam. Margaret Court remains the first woman to complete the calendar-year singles Grand Slam in the Open Era.