When William Marshall Tharp was born on 28 June 1840, in Harrison, West Virginia, United States, his father, Hezekiah D Tharp, was 48 and his mother, Huldah Cox, was 43. He married Martha Matilda Witham on 16 January 1865, in Scotland, Jasper, Missouri, United States. They were the parents of at least 1 son and 1 daughter. He lived in Vernon Township, Van Buren, Iowa, United States in 1900 and Vernon, Van Buren, Iowa, United States in 1910. He died on 10 June 1919, in Mount Sterling, Van Buren, Iowa, United States, at the age of 78, and was buried in Mount Sterling, Van Buren, Iowa, United States.