A duplex typewriting machine had two sets of alphabet keyboards. Credit: Branford House Antiques

Some called it the fastest and best typewriting machine in the world. It was destined to revolutionize the business world. What was this marvelous invention that everyone was talking about in 1893?

It was a duplex typewriter invented and patented by Iowan Adolphus S. Dennis, a former teacher at the Commercial College in Iowa City.


Iowa History, a weekly column, appears at IowaWatch on Saturdays.

Cheryl MullenbachCheryl Mullenbach is the author of non-fiction books for young people. Her work has been recognized by International Literacy Association, American Library Association, National Council for Social Studies, and FDR Presidential Library and Museum.

Visit her website at: www.cherylmullenbachink.com

The design of this novel machine incorporated the use of two sets of keyboards, allowing users to push two keys at the same time. Of course, it greatly increased the speed that a worker could produce documents. People who had used the typewriter claimed they could type an average of ten letters for every second of time. Some business people predicted the amazing new machine would replace the use of shorthand in offices.

The Dennis Duplex Typewriter was showcased at the 1893 World’s Fair in Chicago. It received rave reviews for its performance, style and durability. A fair committee highlighted the machine’s features: it doubled the speed of other typing machines, it could print two different letters of the alphabet as quickly as one letter by the traditional machines, it had two points of contact between the keys and paper, and it was strongly built. Although it was described as a “peculiar” invention, fair goers also called it “ingenious.”

Business machine dealers who witnessed the Dennis typewriter in action at the fair proclaimed it the “finest automatic machinery in the world.” Their endorsements helped Dennis as he looked for additional investors for his factory back in Des Moines. He had plans to employ up to a thousand men within ten years at the factory where his machines would be built.

An Algona newspaper called the Iowa-built product a “wonderful, remarkable invention” that would “revolutionize typewriting.” Described as a “neatly and compactly” built machine, the paper predicted it would give “very long service” to its owners.

The Humeston New Era reported that the typewriter’s World’s Fair exhibition allowed operators from all over the world to see the machine, and they were highly impressed. The paper reported the machine—the “fastest writing machine in the world”—would become world famous. In fact, dealers from South African, South America, New Zealand and Russia were applying to handle the duplex typewriter in their countries. In America nine large cities now had dealers in the new typewriter.

Dennis wined and dined business investors in Des Moines. At one event he gave a lunch for prospective investors. About 150 people showed up to hear about the machine. Dennis said he had already invested $100,000 in his project. He asked attendees to help promote the machine as a “distinctively Des Moines invention.”

An expert typewriter showed off the features of the machine at the lunch, writing a sentence at the rate of 190 words per minute. He claimed he had been using one for a year and at one time had written as many as 206 words a minute on the duplex. It was reported that orders were already coming in for the machine.

George Jewett, a Des Moines businessman, went into business with Dennis; and together they manufactured the duplex machine. Despite predictions, the machine never took off. It was manufactured for only a short time. A classified ad in a 1905 magazine illustrated the value of the machine by 1905: “For sale—Duplex typewriter. Will trade for motor-cycle and pay difference.” Today they are collector’s items.



  • “Dennis Duplex Typewriter,” Daily Citizen (Iowa City), April 28, 1893.
  • “Fastest Writing Machine in the World,” New Era (Humeston, IA), 17, 1894.
  • National Cyclopedia of American Biography, NY: James T. White & Co., p 537, 1906.
  • “News of the State,” New Era, Nov. 15, 1893.
  • The Stenographer, vol. 4, no. 3, July 1893, p 99-100.
  • “A Wonderful Invention,”Algona Upper Des Moines, 27, 1893.

Type of work:

Leave a comment

Your email address will not be published. Required fields are marked *