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Thomas D. O'Brien, Associate Justice 1909-1911

Thomas D. O'Brien

Portrait of Justice Thomas D. O'Brien

O'Brien was one of the founders of the Saint Paul College of Law, now Mitchell Hamline.


Thomas O'Brien was born in LaPointe, on Madeline Island, Wisconsin on February 14, 1859.  He moved to Minnesota with his family when he was just four years old, and grew up in the city of Saint Paul.  He studied law at the firm of Young & Newell before he was admitted to practice law in 1880, and became Clerk of the Municipal Court of Saint Paul that same year. In 1885, he was appointed Assistant City Attorney of Saint Paul, and then in 1891, ran for and was elected Ramsey County Attorney.  During this tenure, he was assisted by a young Pierce Butler, who would later become the first Minnesotan on the U.S. Supreme Court.

After only one year as a prosecutor, O'Brien declined reelection and entered into private practice. In 1905, Governor John A. Johnson appointed O’Brien Insurance Commissioner for the State of Minnesota. He held the position for two years before returning to private practice and establishing the firm of O’Brien & Stone, with fellow future Justice Royal A. Stone.  

On September 1, 1909, Governor Johnson appointed O’Brien Associate Justice of the Minnesota Supreme Court for a term expiring on January 1, 1911. As with other appointments, O’Brien served his appointed term, but returned to private practice as soon has his term was complete. 

O’Brien was well known and well respected within the legal community. He served as the first president of the Saint Paul Association and was one of the founders of the Saint Paul College of Law, now Mitchell Hamline. He also served as Dean of the original Saint Thomas College of Law until its dissolution in 1933. 

Justice O’Brien died at his home in Saint Paul on September 3, 1935. He was memorialized by several prominent members of the legal community of the time, including U.S. Supreme Court Justice, Pierce Butler with whom he had been friends for fifty years.  

You may learn more about the life of Justice O'Brien in the book Testimony: Remembering Minnesota’s Supreme Court Justices, which is the source of this brief biography. 


Image Credit: Portrait of Thomas D. O'Brien from Men in Minnesota: A Collection of the Portraits of Men Prominent in Business and Professional Life in Minnesota, 2nd ed. (St. Paul: R.L. Polk & Co, 1915),   Thomas O'Brien's signature in the Roll of Attorneys, Supreme Court, State of Minnesota, 1858-1970, p. 14. Available online at:

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