Locke Adder

The first American-made adder to enjoy modest commercial success was developed by Clarence E. Locke (1865-1945), a native of Edgerton, Wisconsin, who graduated from Cornell College in Mt. Vernon, Iowa, in 1892. Locke worked for a time as a civil engineer in Minnesota, and then joined his father in operating a lumberyard in Kensett, Iowa.
This early version of the device has a wooden base with grooves for nine sliding metal rods that move crosswise. Each rod represents a digit of a number being added. Protruding knobs on the rods represent different numerals. The rods are held in place by a metal cover that extends over about a third of the right top, and by a metal bracket on the left side. When the device is in zero position, all the rods are in their rightmost position. Numbers are entered by sliding rods to the left, and the result appears in numbers immediately to the left of the metal cover. There is no carry mechanism. The cover is brown, not black or silver-colored as in later Locke adders.
The instrument is marked on the cover: C.E. LOCKE (/) MFG. Co. It is also marked: KENSETT, IOWA. [/] U.S.A. This example came to the Smithsonian from the collection of Felt & Tarrant Manufacturing Company (later Victor Comptometer Corporation).
References: Robert Otnes, “Sliding Bar Calculators,” ETCetera #11 (June 1990): pp. 6-8.
P. Kidwell, “Adders made and Used in the United States,” Rittenhouse, 8, (1994): pp. 78-96.
Currently not on view
date made
C. E. Locke Manufacturing Company
place made
United States: Iowa, Kensett
Physical Description
metal (overall material)
wood (overall material)
overall: 1.5 cm x 28.4 cm x 11.1 cm; 19/32 in x 11 3/16 in x 4 3/8 in
ID Number
catalog number
accession number
Credit Line
Gift of Victor Comptometer Corporation
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History


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