Davis was born in Clarksburg, West Virginia. He represented West Virginia in the United States House of Representatives from 1911 to 1913. He served as United States Solicitor General from 1913 to 1918 and as ambassador to the United Kingdom from 1918 to 1921. He was also a constitutional lawyer. Davis argued 140 cases before the United States Supreme Court, more than anyone had argued to that time, including a defense of the separate but equal doctrine in Brown v. Board of Education.