Who was the first woman to hold the rank of U.S. Ambassador?

The answer is:

Eugenie Moore Anderson was appointed U.S. Ambassador to Denmark on October 20, 1949. She presented her credentials on December 22, 1949, and served until January 19, 1953. [source: U.S. State Department]

Yesterday's question:

Who was the first U.S. ambassador to Vietnam, following restoration of diplomatic ties?

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