He is in the 1870 CA census, but in 1880 his wife is listed as widow. Names of his children show. From familysearch.org.
https://familysearch.org/pal:/MM9.1.1/MN6G-MN4
United States Census, 1870 California Sacramento Dry Creek
Name: Wm Randolph
Household Gender/Age/Birthplace
Wm Randolph M/48y/IL
Mary Randolph F/43y/IL
Wm G Randolph M/17y/CA
John S Randolph M/15y/CA
Frank Randolph M/13y/CA
Mary Randolph F/12y/CA
Harriett S Randolph F/10y/CA
Margarett A Randolph F/8y/CA
Samuel Randolph M//5y/CA
Michel B Randolph M/3y/CA
https://familysearch.org/pal:/MM9.1.1/M6PQ-BQ2
United States Census, 1880 Dry Creek, Sacramento, California
Martial Status: Widowed
Age (Expanded): 55 years
Occupation: Farming
SELF M. Randolph F/55/IL/IL/IL
SON Samuel Randolph M/16/CA
SON M. B. Randolph M/12/CA
DAU Lizzie Randolph F/9/CCA