Miller worked as secretary to U.S. Representative William H. Heald from 1910 until 1912, and during this period studied law in Washington, D.C. He was appointed by his father, Governor Charles R. Miller, to the position of Delaware Secretary of State from 1913 until 1915.
Miller was elected to the United States House of Representatives in 1914, defeating incumbent Democratic U.S. Representative Franklin Brockson. During this term, he served in the Republican minority in the 64th Congress. Seeking reelection in 1916, he lost to Democrat Albert F. Polk, a lawyer from Georgetown. Miller served from March 4, 1915, until March 3, 1917, during the administration of U.S. President Woodrow Wilson.
Miller served in the administration of United States President Warren G. Harding, but was convicted in 1927 of conspiring to defraud the U.S. government.[2] The conviction concerned Miller's service as Alien Property Custodian and the effort by Metallgesellschaft AG of Germany to overturn the U.S. government's confiscation of its interest in the American Metal Company during World War I.[3][4][5] He served 18 months in prison and was paroled in 1929 and pardoned by United States President Herbert Hoover in 1933.
Later life and death
At this point, Miller moved to Reno, Nevada, where he spent the rest of his life. There he became the founder of Nevada State parks system and served as chairman of the Nevada State Park Commission in 1935, 1936, from 1953 to 1959, and from 1967 to 1973. He also continued his activity in veterans affairs as staff field representative of the United States Veterans Employment Service from 1945 until 1957. He died in Reno on May 5, 1973, and was buried in the Masonic Memorial Gardens in Reno.