I did an Ancestry.com Federal Census search and found these two, could not find him in the 1900 census.

1870 Federal Census

William Miller, age 35, Farmer, wife Martha A., 28, George 8, Edward T. 4, Mary E. 4, Sarah E. 2
Townships 9 and 10 West or Rf, Copiah, Mississippi, Post Office - Linden

1880 Federal Census

William H. Miller, age 45, Farmer, Martha A, 33, George H. 16, Sarah E. 11, Walter E. 5
Beat 1, Jefferson, Mississippi