1910 census: He and Annie were in Justice Precinct 2, Jones Co., Texas. They are white.
He can't be: 1920 census: Los Angeles, California; 515 Ceres Avenue: Saunders, William M., male, black, 47, married [but no wife with him], b Texas; father b. TX; mother b. Louisiana; general merchant; appears to be living in a boarding house.
Could he be: 6 May 1922: Leavenworth, Kansas: US Penitentary, Name index to inmage case files, 1895-1931; Inmate #17889 (William M. Saunders)
[Of interest is that there is a 22 Nov 1922 case file, same prison for a William R. Saunders...]
W. M. Saunders, Texas Court of Criminal Appeal Indexes, 1892-1947, Primitive Number 47, (1892-1909), p 92
There are many records of Texas-born William Saunders without the "M".