Born in Newport, Rhode Island. Received AB. from Harvard in 1904 and LL.B. in 1907. Married Margaret Stuyvesant Rutherford September 20, 1911. They were divorced in 1919. Admitted to the New York bar in 1924. Married Dorothy Randolph Fell September 2, 1924. He had no children. Received commission as captain in U. S. Army. Served with AEF in France.

Elected to the House of Representatives and served March 4, 1921, to March 3, 1927. Appointed as Undersecretary of the Treasury March 4, 1927, to February 11, 1932. Appointed Secretary of the Treasury by President Hoover and served February 13, 1932, to March 4, 1933. He died in New York City.

Mills appears on a medal (USM 212) as one of the series for Secretaries of the Treasury. Dies were by John Ray Sinnock. Mills appears on the Assay Commission Medal of 1933 (AC-78). The obverse was by John Sinnock and reverse by Adam Pietz.

bio: BDC; BDEB; DAB; Failor; NCAB 32; WWWA-1