Hollerith's punched-card tabulator wins the census contract
A former census clerk builds a machine that reads holes in cards with mercury and electricity
Quick facts
- Inventor
- Herman Hollerith
- Year
- 1890 US census
- Mechanism
- Punched cards read via pins completing a mercury-cup circuit
- Later company
- CTR (1911), renamed IBM in 1924
What happened
The 1880 US census had taken more than eight years to fully tabulate by hand, and the Census Bureau ran a competition to find a faster method for 1890. Herman Hollerith, a former Bureau employee, won it with a machine that read data punched as holes in paper cards. Operators pushed spring-loaded pins through the card; where a hole let a pin pass through, it dipped into a small cup of mercury below and completed an electrical circuit, which advanced a dial on the tabulator counting that category. An average operator could process about 7,000 cards a day, roughly ten times faster than tallying by hand.
Why it matters
Hollerith's company later merged with others to form the Computing-Tabulating-Recording Company in 1911, which was renamed International Business Machines in 1924. Punched cards built on his design remained the standard way to feed data and programs into computers for the next seventy years, well into the era of mainframes.
How we know
The Computer History Museum's history of the punched card describes Hollerith's design, the mercury-cup circuit, and the processing speed from its own collection notes and historical records.
Sources
- Computer History Museum. Making Sense of the Census: Hollerith's Punched Card Solution · Reputable sourcecomputerhistory.org · The domain "computerhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- U.S. Census Bureau. The Hollerith Machine · Reputable sourcecensus.gov · The domain "census.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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