Roberts: How the U.S. Census came to drive computer development

Of St. George’s Community College





A minimalist interpretation of the mission would require reporting only the overall population of each state. But the census has never confined itself to this.


The first census, in 1790, also made  distinctions by age and gender that were not constitutionally mandated. In subsequent decades, many other personal attributes were added — occupational status, marital status, educational status, place of birth and so on.

As the country grew, each census required greater effort than the last, not merely to collect the data, but also to compile it into usable form. As a consequence, the processing of the 1880 census was not completed until 1888.

It had become a mind-numbingly boring, error-prone, clerical exercise of a magnitude rarely seen before. Since the population was evidently continuing to grow at a rapid pace, those with sufficient imagination could foresee that processing the 1890 census would be gruesome indeed without some change in procedure.


On Sept. 23, 1884, the U.S. Patent Office recorded a submission from the 24-year-old Hollerith titled, “Art of Compiling Statistics.” By progressively improving the ideas represented in this initial submission, Hollerith would decisively win an 1889 competition to improve the processing of the 1890 census.

The technological solutions devised by Hollerith involved a suite of mechanical and electrical devices. The first crucial innovation was translating data on handwritten census tally sheets to patterns of holes punched in cards.

As Hollerith phrased it, in the 1889 revision of his patent application, “A hole is thus punched corresponding to person, then a hole according as person is a male or female, another recording whether native or foreign born, another either white or colored, etc.” This process required developing special machinery to ensure holes could be punched with accuracy and efficiency.

Hollerith devised a machine to “read” the card by probing it with pins. Only where there was a hole would the pin pass through the card to make an electrical connection, resulting in advance of the appropriate counter.

For example, if a card for a white male farmer passed through the machine, a counter for each of these categories would be increased by one. The card was made sturdy enough to allow passage through the card-reading machine multiple times, for counting different categories or checking results.



The company he founded, the Tabulating Machine Company, would, after he retired, become International Business Machines — IBM for short. IBM led the way in perfecting card technology for recording and tabulating large sets of data for a variety of purposes.

By the 1930s, many businesses were using cards for record-keeping procedures, such as payroll and inventory. Some data-intensive scientists, especially astronomers, were also finding the cards convenient. IBM had by then standardized an 80-column card and developed keypunch machines that would change little for decades.


Those who have grown up knowing computers only as easily portable devices, to be communicated with by finger touch or even voice, may be unfamiliar with the room-size computers of the 1950s and ’60s, where the primary means of loading data and instructions was by creating a deck of cards at a keypunch machine, and then feeding that deck into a card reader. This persisted as the default procedure for many computers well into the 1980s.


Hopper was an important member of the team that created the first commercially viable general-purpose computer, the Universal Automatic Computer or UNIVAC, one of the card-reading behemoths. Appropriately enough, when the first UNIVAC was delivered in 1951, it was sent to the U.S. Census Bureau, which was still hungry to improve its data processing capabilities.

No, computer users would not use punched cards forever. But they used them through the Apollo moon landing program and much of the Cold War. Hollerith would likely have recognized the direct descendants of his 1890s census machinery almost 100 years later.

From The Conversation, an online repository of lay versions of academic research findings found at https://theconversation.com/us . Used with permission.