
Key Points:
- Very little is known about Milton Hinkle outside of his invention of a simple adding machine, other than that his father was a steamboat owner on the Ohio River.
- Hinkle’s simple adding machine, patented in 1878, is a similar design to those of Jabez Burns and John Ballou, and the prototype survives in the National Museum of American History in Washington, D.C.
- The patent model features wooden sides and a brass strip covering the front, bottom, and back. The top of the instrument is curved at the front to the shape of two wheels that rotate inside, while a strip of wood between the wheels shows the digits from 1 to 9.
Who Was Milton Hinkle?
Milton Hinkle was an inventor born in 1848 in Carrollton, Carroll County, Kentucky. Milton was popular for his invention of the simple adding device, a device patented on March 5, 1878.
Milton’s simple adding device was somewhat similar to the earlier devices of Jabez Burns and John Ballou, with its patent model surviving our time and still preserved in the collection of the National Museum of American History in Washington, D.C.
Quick Facts
- Full Name
- Milton Hinkle
- Birth
- January 8, 1848
- Net Worth
- N/A
- Children
- N/A
- Nationality
- American
- Place of Birth
- Carrollton, Carroll County, Kentucky
- Fields of Expertise
- [“Inventor”]
- Institutions
- N/A
- Contributions
- Simple Adding Machine
Milton’s death date isn’t available for public knowledge.
Early Life
The information about Milton Hinkle is very scarce, with close to nothing recorded about his early life, education, etc.
Nonetheless, history shows that Milton was born on January 8, 1848, in Carrollton, Carroll County, Kentucky, to Milton Washington Hinkle and Nancy Kennedy Hinkle. His father, Washington, was born in 1810 in Louisville, KY, and was a steamboat owner on the Ohio River.
Career
Phase 1
As mentioned earlier, apart from his invention of the simple adding machine in 1877, almost nothing is known about the inventor, including his career journey. However, since his father was a steamboat owner, we can safely say that he supported his father’s business, perhaps while he was a kid, before his invention.
What Did Milton Hinkle Invent?
Invention 1 – Milton Hinkle’s Adding Machine
Milton Hinkle invented the simple adding machine in 1877 while living in Memphis, Tennessee. The adding machine was patented on March 5, 1878 (US patent 200911), almost a year after the invention.

The machine was somewhat similar to the earlier devices of Jabez Burns and John Ballou. The patent model of the device survived to our time and is kept now in the collection of the National Museum of American History in Washington, D.C.
The patent model has wooden sides and a brass strip covering the front, bottom, and back. The instrument’s top is curved at the front to the shape of two wheels that rotate inside it. A strip of wood between the wheels has the digits from 1 to 9 marked on it.
Each wheel has the digits from 0 to 9 marked on it three times. A pin protrudes from the wheel between each digit, and each tenth pin is slightly longer than the others. The spacing of the digits is the same as that on the case.

The large wheels are linked to two smaller toothed wheels at the back of the instrument. These smaller wheels are marked with the numbers from 0 to 13 and are meant to move forward every time the large wheel passes a longer “10” pin, recording numbers that should be carried. This simple adding device doesn’t have separate wheels for registering results.
The operator places his finger upon the pin of the wheel opposite the index number representing the figure to be added and turns the said wheel until his finger strikes the finger-plate, all the wheels being adjusted before beginning with their zeroes in the first place above the plates D E.
Milton Hinkle: Marriage, Divorce, Children, and Personal Life
Marriage
No history book or resource states whether Milton Hinkle was married or otherwise. However, we would continue updating this page whenever any new information about the inventor is discovered.
Children
Neither the marriage life nor the children of Milton were recorded. Therefore, it’s difficult to state whether Milton Hinkle has any child or otherwise.
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