A granddaughter of the pioneer Linville family who first settled in Arizona in the late 1880s, she won the title of Miss America in 1949.

She married and divorced her high school sweetheart, Douglas Cook, during her reign as Miss America.

After this, a rule was enacted which requires Miss America contestants to sign a pledge vowing they have never been married or pregnant.

While a student at the Arizona State College at Tempe, Mercer acted in a professional stage production of Hay Fever at the Sombrero Playhouse in Phoenix during February 1953, alongside Miriam Hopkins, Wilton Graff, and George Nader.

In January 1978 she married William Marvin Gillespie in Los Angeles.