Monroe Calculating Machine Company

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The Monroe Calculating Machine Company was a maker of adding machines and calculators founded in 1912 by Jay Randolph 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.


Portrait of Jay Randolph Monroe

In 1911,[1] Jay Randolph Monroe first saw the Baldwin Calculator, the invention of Frank Stephen Baldwin. Although Mr. Baldwin's machine had been patented in 1874 and had been judged by the Franklin Institute as the most noteworthy invention of that year winning the John Scott Medal,[2][3] it had not been developed for commercial use. Mr. Monroe recognized the merits of the Baldwin Calculator, and in April 1912 he organized the Monroe Calculating Machine Company, and in a small rented room near Newark, New Jersey, the manufacture of the first Monroe Adding-Calculator was begun.

The following year the firm moved to Orange, New Jersey. The factory personnel consisted of only nine men and the entire heavy factory equipment was a lathe and two small presses. Even with these meager tools, tolerances were maintained to within thousandths of an inch to insure the accurate performance of the finished machine. The first Monroe was offered to the business world in 1914.

In 1932, the company was awarded the Franklin Institute's John Price Wetherill Medal.[4]

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.[5] 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.[6] 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.


Mechanical and Electromechanical Calculators[edit]

Monroe L-160

Early models of calculator were designated by letters.[1] The letters A, B, and C are lost in the records of those early days devoted to constructing a suitable pilot model. The "D" model started manufacture in 1915 with serial numbers below 4,000. The "E" model started manufacture in 1916 with serial numbers beginning at 4,000. The "F" model was introduced in 1917 with serial numbers above 6,000.[7] The "G" model was the first machine of the refined style, and was introduced in 1919 with serial numbers above 20,000.[7] The "H" and "I" were never released for production. The "K" was the real start of the big forward march by the Monroe Company. The "K" hand machine, introduced in 1921, was followed by KA, KAS, KAA, KASC, KASE, etc., machines all more fully automatic than the former. The "L" model was produced from January 1929 to February 1971.[8] The "M" model further refined the "L".

Model 145 was the last adding machine model produced.
Model 570 was the last electro-mechanical four-function calculator model produced.

Electronic Calculators[edit]

Monrobot XI
  • 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.
    • Monrobot III - general-purpose computer, public debut in 1952 on the TV broadcast of the national election results over the NBC network.[9][10]
    • Monrobot V - portable, general-purpose, used by military for surveying and mapmaking, 1955[11][12][13]
    • Monroe Calculating Machine Mark XI (or "Monrobot XI") was an inexpensive, relatively slow, general-purpose computer introduced in 1960


  1. ^ a b Monroe Service Training Course (Apprentice) Book Number 1: Introduction to our Company and Function-Adjustment LN model Calculator. Monroe Calculating Machine Company. 1957. Retrieved 4 June 2016.
  2. ^ "The Romance of the Monroe Calculating Machine". The International Office Equipment Magazine. 38: 52. January 1918. Retrieved 5 June 2016.
  3. ^ Fox, Robert (9 Dec 1968). "The John Scott Medal" (PDF). Proceedings of the American Philosophical Society. 112 (6): 423. Retrieved 5 June 2016.
  4. ^ "Monroe Calculating Machine Co". The Franklin Institute. Retrieved 5 June 2016.
  5. ^ The New York Times, January 24, 1958, p. 31.
  6. ^ The Wall Street Journal, March 15, 1972, p. 40.
  7. ^ a b McCarthy, J. H. (1924). The American Digest of Business Machines. American Exchange Service. pp. 80–81. Retrieved 7 June 2016.
  8. ^ Sheridan, James (May 1971). "The L model calculator ends a 42-year career". Monroe Newsletter (May 1971). Retrieved 4 June 2016.
  9. ^ "9. The MONROBOT". Digital Computer Newsletter. 5 (2): 6. Apr 1953.
  10. ^ Battle of the Brains: Election-Night Forecasting at the Dawn of the Computer Age. MONROBOT I: pp. 234, 237; MONROBOT III: pp. 237-242, 266-267, 437. 2010.
  12. ^ Research, United States Office of Naval (1953). A survey of automatic digital computers. Office of Naval Research, Dept. of the Navy. p. 67 (73).
  13. ^ Weik, Martin H. (Mar 1961). "MONROBOT V". A Third Survey of Domestic Electronic Digital Computing Systems.

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]