Mary Pauline Hartline was born in Hillsboro, Illinois in 1926, the second child and second daughter of Paul and Dorothy Crowder Hartline. Her father was involved in local politics, becoming chairman of the Montgomery County Democratic Party and, after Franklin D. Roosevelt was elected president, the Hillsboro postmaster. Mary graduated from Hillsboro High School, where she was elected the "Queen of Love and Beauty" (then the equivalent of the prom queen).
Harold Stokes was a Montgomery County native who had gained success as a band leader and radio personality. During a period that he was out of broadcasting, he was living near Hillsboro and was persuaded to produce a local amateur show fund-raiser. Mary was a dancer in the show.
Upon graduating from high school, with the encouragement of Stokes, Mary moved to Chicago with the intent to become a model. In 1946, she was cast in ABC radio's Teen Town (originally, Junior Junction) (or vice versa; references disagree). The cast of this show, produced by Harold Stokes, included Dick York as the mayor of a town inhabited only by teenagers. While appearing on this show, Mary was stricken with a severe case of polio, but quickly recovered. Soon thereafter, the twenty-one year old Mary married the forty-two year old Stokes.
In 1949, the ABC television network picked up the local show, Super Circus, which was also produced by Stokes. Mary moved to Super Circus where her looks and figure made her a national star and a sex symbol for thousands of boys, young and old. The show, starring former real-life circus barker Claude Kirchner, featured Mary as the band leader, the circus clowns Cliffy, Scampy, and Nicky, as well as Mike Wallace playing the circus barker peddling Peter Pan Peanut Butter.
Super Circus was a hit, on the cover of TV Guide, produced in Chicago through 1955, when the network moved it to New York, replacing Kirchner with Jerry Colonna and Mary with Sandy Wirth for what was the show's final season. Hartline, however, made the best of her years on the show, marketing her own line of dolls, clothes, boots, et cetera--- three dozen different Mary Hartline products. In 1951, she also hosted a short-lived Mary Hartline Show on ABC TV that failed to find a sponsor.
Following the network's decision to move Super Circus to New York, Mary returned to local Chicago TV in 1957 with Princess Mary's Magic Castle which aired for a year and a half. Thereafter, Hartline retired from show business. She was enshrined in Chicago's Museum of Broadcast Communications in 2012.
Hartline's marriage to Stokes ended in divorce in 1951. She then was married to George Barnard, her tax lawyer, until 1960. After divorcing Barnard, she wed Chicago building contractor George Carlson, who died shortly thereafter. Finally she was married to Woolworth heir Woolworth Donohue until his death in 1972. The Donohues were yachting enthusiasts and fixtures of the "old money" set in Palm Beach and Southampton, where Mary remained for many years. More recently, she has returned to residing in her home town of Hillsboro.