Monroe Calculator Company

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The Monroe Calculator Company was a maker of adding machines and calculators founded in 1912 by Jay R. Monroe based on a machine designed by Frank Stephen Baldwin. Now known as Monroe Systems for Business, the company was also known as Monroe Calculating Machine Company, Monroe THE Calculator Company, and Monroe Division of Litton Industries.


For many years, Monroe was headquartered in Orange, New Jersey and Morris Plains, New Jersey with its manufacturing plants in New Jersey, Bristol, Virginia and Amsterdam. In 1958, the company was acquired by Litton Industries.[1] Litton sold it in 1984. In the mid-1980s, the company diversified and began carrying a line of private-labeled copiers (manufactured by Mita Corp.) and cross-cut paper shredders, but those items have been discontinued.

In the 1970s and 1980s, the company had some 300 sales and service branch offices in the United States. In 1972, Monroe announced a pocket-sized electronic display calculator at $269.[2] As low cost electronic calculators from Japan became readily available through retail distribution, the mechanical calculator companies like Monroe, Friden, and Marchant declined even as they introduced programmable calculators.


Monroe L-160
Monrobot XI
  • Hand-crank models; almost all manual models had an electrically driven version. The most famous and successful machine was the "Series L", produced since 30s until 60s in several variants and models
  • Electromechanical models; rotary calculator display models and printing models
Model 145 was the last adding machine model produced.
Model 570 was the last electro-mechanical four-function calculator model produced.
  • Electronic calculator models
Visual Display only
400 and 600 series
Paper tape and visual display
1300 and 1400 series
  • Programmable models
The 1600 and 1800 series calculators, from OEM Compucorp competed against similar desktop calculators from Wang Laboratories.
Model 200 billing machine for accounts receivable functions.
Monroe Calculating Machine Mark XI (or "Monrobot XI") was an inexpensive, relatively slow, general-purpose computer introduced in 1960


  1. ^ The New York Times, January 24, 1958, p. 31.
  2. ^ The Wall Street Journal, March 15, 1972, p. 40.

Further reading[edit]

  • New York Times; December 2, 1964, Wednesday; The division of Litton Industries in The Monroe International introduced an electronic desk-top calculator yesterday that it hopes will fill the market gap between adding machines and computers.
  • New York Times; August 17, 1969, Sunday; Tiny Calculator in Production. The Monroe division of Litton Industries, Inc., has begun production of what it describes as the smallest cathode ray tube desk calculator in the world. Donald A. McMahon, president, said the new unit, which weighs 14 pounds and measures 11 inches wide by 17 inches deep, is made entirely in this country with no parts from foreign countries.

External links[edit]