Tabulating Machine - 1890 Census

1890 Census

The 1880 census had taken seven years to tabulate, and by the time the figures were available, they were clearly obsolete. Due to rapid growth of the U.S. population from 1880 to 1890, primarily because of immigration, it was estimated that the 1890 census would take approximately 13 years to complete—an immense logistical problem. Since the U.S. Constitution mandates a census every ten years to apportion taxation between the states and to determine Congressional representation, a faster method was necessary.

In the late 1880s Herman Hollerith, inspired by conductors using holes punched in different positions on a railway ticket to record traveler details such as gender and approximate age, invented the recording of data on a machine readable medium. Prior uses of machine-readable media had been for control (e.g. automatons, piano rolls, looms), not data. "After some initial trials with paper tape, he settled on punched cards..." Hollerith used punched cards with round holes, 12 rows and 24 columns. His machines used relays (and solenoids) to increment mechanical counters. A set of spring-loaded wires were suspended over the card reader. The card sat over pools of mercury, pools corresponding to the possible hole positions in the card. When the wires were pressed onto the card, punched holes allowed wires to dip into the mercury pools, making an electrical contact that could be used for counting, sorting, and setting off a bell to let the operator know the card had been read. The tabulator had 40 counters, each with a dial divided into 100 divisions, with two indicator hands; one which stepped one unit with each counting pulse, the other which advanced one unit every time the other dial made a complete revolution. This arrangement allowed a count up to 10,000. During a given tabulating run, counters could be assigned a specific hole or, using relay logic, a of combination of holes, e.g. to count married females. If the card was to be sorted a lid for a compartment of the sorting box would open for storage of the card, the choice of compartment depending on the data in the card.

Hollerith's method was used for the 1890 census. The cards were coded for age, state of residence, gender, and other information; clerks punched holes in the cards to enter information from returns. The census results were "... finished months ahead of schedule and far under budget".