Born in LaPointe, on Madeline Island, Wisconsin on February 14, 1859, Thomas D. O’Brien moved to Minnesota when he was just four years old. O’Brien grew up in Saint Paul and studied law at the firm of Young & Newell. He was admitted to practice law in 1880, and became Clerk of Municipal Court of Saint Paul that same year. In 1885, he was appointed Assistant City Attorney and then in 1891, ran for and was elected Ramsey County Attorney.
After one year as a prosecutor, he decline reelection and entered into private practice. In 1905, Governor John A. Johnson appointed O’Brien Insurance Commissioner. He held the position for two years before returning to private practice and establishing the firm of O’Brien & Stone, with 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 in the legal community. He served as the first president 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 Saint Thomas College of Law until its dissolution.
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 read more about the life and work of Justice O’Brien in the memorial linked below, or in the book Testimony: Remembering Minnesota’s Supreme Court Justices, which is the source of this brief biography.