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Maureen Connolly of the United States in 1953.
In her short (five year) professional career in women's tennis, Maureen Connolly won tournament after tournament, proving herself to be one of the all-time great singles women tennis players. Born on September 17, 1934, Connolly was 10 years old when she first picked up a racket. She entered her first competition soon after. When she was 14, she became the youngest girl ever to win the national junior tennis championship. She entered the women's league in 1950, racking up titles; in 1953, she became the first and youngest woman to win the Grand Slam. Just a year later, a horseback-riding accident resulted in an injury to her leg that made it impossible for Connolly to continue to play competitively.