Amos Cowgill Mendenhall was born on November 16, 1828, in Clinton County, Ohio, to Hiram Mendenhall and Martha Ann Hale.
Some sources suggest that he worked as a store manager, manufactured goods, farmer, and mechanic around Indiana after he returned home from their California Gold Rush adventure.
In 1867, Amos Mendenhall of Cerro Gordo, Indiana, patented a practical calculator (US patent 67786). The practical calculator of Amos Mendenhall is an adder with a brass box that has a rotating disc inset on the top.
Mendenhall not only patented the practical calculator which was his first, but he also took out patents for gold mining devices, a tricycle, and a bicycle granted on September 29, 1903.