On 13 January 1874, Cyrus G. Spalding, a Boston bookkeeper, received US Patent No. 146,407 for an “Improvement in adding-machines”.
Spalding’s goal was practical office arithmetic made mechanical, with a design meant to be simple, affordable, and reliable.
The patent sits on the early pathway from bookkeeping aids to calculators and, eventually, computers.
Drawings from US Patent No. 146,407 for an “Improvement in adding-machines” and the Spalding Adding Machine user instructions.
| Country | Kind | No. | Published | Title | Download |
|---|---|---|---|---|---|
| US | Patent | 146,407 | 13.01.1874 | Improvement in adding-machines |
Last updated on 18 February 2026