Conversation so far:
What happened at the early stage of Billie's career?
at the French Open in 1972 made her only the fifth woman in tennis history to win the singles titles at all four Grand Slam events, a "career Grand Slam..
How did her career end?
CANNOTANSWER.
Did she win any award or recognition?
King won a record 20 career titles at Wimbledon - six in singles, 10 in women's doubles, and four in mixed doubles.

Question: Which of her awards is the most notable?
Self-contained rewrite: Which of Billie Jean King's awards is the most notable?