Mobley was born in 1937 in Biloxi, Mississippi. After serving her reign as Miss America 1959, Mobley embarked on a career in both film and television. She signed a five-year contract with MGM. She made her first television appearances on Be Our Guest in 1960, followed by five appearances on Burke's Law from 1963 to 1965, and went on to make multiple appearances on Perry Mason, Love, American Style and Fantasy Island. She had a recurring role as Maggie McKinney Drummond on Diff'rent Strokes in the final season of the series, having taken over the role from Dixie Carter. She would later guest star as Karen Delaporte, a snide head of an historical society who crossed swords with Dixie's character, Julia Sugarbaker, in Carter's later series, Designing Women. She made two films with Elvis Presley in 1965, Girl Happy and Harum Scarum . They were friends as they were both from Mississippi. Elvis liked that Mary Ann was a true southern lady.