Why was Tammy Wynette known as the “first lady of country music”?

Tammy Wynette was known as the “first lady of country music” from the late 1960s to the 1990s because of her career as one of the most successful female vocalists in the history of the genre. Her recordings had sales of more than $100 million, and she had 20 number-one hits throughout her career, including the 1968 single “Stand by Your Man.”