Elkins was an industrialist with interests in railroads, banking, utilities, and coal mining; he was appointed as a Republican to the U.S. Senate to fill the vacancy caused by the death of his father, Stephen Benton Elkins, and served from January 9 to January 31, 1911, when a successor was elected. During World War I he served as a major with the 7th Division of the United States Army in France, 1917–1918. He was then elected to the U.S. Senate and served from March 4, 1919, to March 3, 1925; he was not a candidate for renomination in 1924. While in the Senate he was chairman of the Committee on Expenditures in the Department of Commerce (Sixty-sixth Congress).
Davis Elkins' father, Stephen B. Elkins, and his grandfather, Henry Gassaway Davis, were both U.S. senators from West Virginia. He was married to Mary Reagan Elkins and had 3 children. His sister Katherine Hallie "Kitty" Elkins (Jan. 14, 1886 – Sept. 3, 1936) was engaged for some time to Prince Luigi Amedeo, Duke of the Abruzzi (1873–1933), a cousin of the king of Italy.