Born Clara Dickey, the daughter of Isaac B. and Hattie (Mudgett) Dickey, aboard the Willard Mudgett—an American ship captained by her father, and docked in Hong Kong harbor. Her parents settled in Quincy, Massachusetts, by 1880.
Clara moved from Boston to New York City by 1900 to pursue an acting career. Her first professional appearance came in 1901, when she was cast as Jehanneton in the play If I Were King, which ran at Garden Theatre (an early component of Madison Square Garden). In 1911 she made her first movie, appearing in the short, silent film The Maid's Double. Blandick finally broke onto Broadway in 1912, when she was cast as Dolores Pennington in Widow By Proxy which ran through early 1913 at George M. Cohan's Theatre on Broadway.
She would continue to achieve success on the stage, playing a number of starring roles, including the lead in Madame Butterfly. By 1914 she was reappearing on the silver screen, this time as Emily Mason in the film Mrs. Black is Back.
In 1929, Blandick moved to Hollywood. By the 1930s, she was well-known in theatrical and film circles as an established supporting actress. Though she landed roles like Aunt Polly in the 1930 film Tom Sawyer (a role she reprised in the 1931 film Huckleberry Finn), she spent much of the decade as a character actor, often going uncredited. At a time when many actors were permanently attached to a single studio, Blandick played a wide number of bit parts for almost every major Hollywood studio (though she would later be under contract with 20th Century Fox). In 1930, she acted in nine different films. In 1931 she was in thirteen different films. As is the case with some other busy character actors, it's impossible to make an exact tally of the films in which Clara appeared. A reasonable estimate would fall between 150 and 200.
In 1939, Blandick landed her most memorable minor role yet – Auntie Em in MGM's The Wizard of Oz. Though it was a small part (Blandick filmed all her scenes in a single week), the character was an important symbol of protagonist Dorothy's quest to return home throughout the film. (Auntie Em and Uncle Henry are the only characters from the beginning of the movie not to have true alter ego characters in the Land Of Oz). Blandick beat out May Robson, Janet Beecher, and Sarah Padden for the role, and earned $750 per week. Some believed Auntie Em's alter ego was to be the Good Witch of the North but opted to use different actresses for each role rather than have a dual role for this. The reason was they wanted someone younger looking to contrast the good witch from the bad witches. Ironically, Billie Burke, who played the Witch of the North, was only 8 years younger than Blandick.
Though the Auntie Em character proved memorable to audiences, few fans knew Blandick's name. She was not billed in the opening credits and is listed last in the movie's closing credits.
After The Wizard of Oz, Blandick returned to her staple of character acting in supporting and bit roles. She retired from acting at the age of 69 and went into seclusion at the Hollywood Roosevelt Hotel.
Throughout the 1950s, Blandick's health steadily began to fail. She started going blind and began suffering from severe arthritis. On April 15, 1962, she returned home from Palm Sunday services at her church. Her residence was 1735 North Wilcox Avenue, Los Angeles, California. She began rearranging her room, placing her favorite photos and memorabilia in prominent places. She laid out her resume and a collection of press clippings from her lengthy career. She dressed immaculately, in an elegant royal blue dressing gown. Then, with her hair properly styled, she took an overdose of sleeping pills. She lay down on a couch, covered herself with a gold blanket over her shoulders, and tied a plastic bag over her head. Clara left the following note: “I am now about to make the great adventure. I cannot endure this agonizing pain any longer. It is all over my body. Neither can I face the impending blindness. I pray the Lord my soul to take. Amen.”
Her landlady, Helen Mason, found her body Sunday morning. In preparing to die, Clara disposed of all her medicines the previous week. She told James Busch, a friend for many years, that they might be discovered if anything happened to her.
She was interred at the Great Mausoleum, Columbarium of Security (Niche 17230) at Forest Lawn Memorial Park Cemetery, Glendale. Blandick was survived by a niece, Mrs. Katherine Hopkins, of Hayward, California. The actress was married Dec. 7, 1905, in Manhattan, to mining engineer Harry Staunton Elliott. They separated by 1910, and are said to have divorced in 1912. They had no children.