Thomas Day Thacher, born September 10, 1881 in Tenafly, New Jersey, was the oldest of four children to Thoams Thacher and Sarah McCulloh (Green) Thacher. Thomas' father was a prominent lawyer in the city of New York. Thacher attended Taft School and Phillips Academy of Andover, Connecticut for his preparatory education, before following his family tradition and attending Yale. After graduating from Yale in 1904, Thacher attended Yale Law School for two years, but left before obtaining his degree. In 1906, he was admitted to the New York bar and joined his father's practice, Simpson, Thacher & Bartlett. Thacher remained with the firm and was made a partner in 1914.
Thacher's career in public service began when he was appointed Assistant U. S. Attorney for the Southern District of New York in 1907, at the age of 26. While in this position, Thacher was recognized for his work in prosecuting customs fraud. After the U.S. entered World War I, he worked with the American Red Cross in Russia from 1917-1918. From 1925-1930, Thacher served as a federal judge on the U.S. District Court for the Southern District of New York, having been appointed by President Coolidge. He was instrumental in investigating the operation of the bankruptcy laws in New York City. His reports to President Hoover were the basis for amendments to the law that extended the control of the courts over bankruptcy proceedings and speeded up the settlement process, thereby reducing any opportunities for abuses.
In 1930, Thacher was appointed by President Hoover to serve as solicitor general. Thacher served as SG until May 1933, at which time he returned to his New York legal practice. He helped create the movement that made possible the election of Fiorello H. La Guardia as mayor of New York. La Guardia appointed Thacher to serve as the leader on the commission to write a new city charter and to the city's corporation counsel in 1943. Soon afterward, Governor Thomas E. Dewey asked Thacher to fill a position on the New York State Court of Appeals, where he served for fourteen years.
Thacher also served as a fellow of the Yale Corporation from 1931-1949, president of the Association of the Bar of the City of New York from 1933-1935, and was a member of numerous social clubs. He first married Eunice Booth Burall, and had three children: Sarah Booth (Storm), Mary Eunice (Brown), and Thomas. After Eunice's death in 1943, Thacher married Eleanor M. Lloyd on July 20, 1945. On November 12, 1950 Thacher died at the age of sixty-nine of a coronary thrombosis at his home in New York city. He was buried in Brookside Cemetery, in Englewood, N.J.