The Census Bureau continued to use updated versions of Herman Hollerith's 1890 electric counting machine through the 1940 census. Processing and tabulation technology took a great leap forward during World War II, when the War Department (precursor to the Department of Defense) began to explore the use of electronic digital computers to process ballistic information. After the war, many of that project's engineers foresaw the peacetime benefits of such a device: computers had the ability to far outstrip the processing speed of older non-digital counting machines. Their efforts brought the Census Bureau into the computer age.

In 1943, the National Defense Research Council (NDRC) approved the design and construction of the Electronic Numeric Integrator and Computer (ENIAC) to be used by the War Department's Ballistic Research Laboratory. The computer was built over the course of three years by a team of engineers led by John W. Mauchly and his former student J. Presper Eckert.

During ENIAC project, Mauchly met with several Census Bureau officials to discuss non-military applications for electronic computing devices. In 1946, with ENIAC completed, Mauchly and Eckert were able to secure a study contract from the National Bureau of Standards (NBS) to begin work on a computer designed for use by the Census Bureau. This study, originally scheduled for six months, took about a year to complete. The final result were specifications for the Universal Automatic Computer (UNIVAC).

UNIVAC was, effectively, an updated version of ENIAC. Data could be input using magnetic computer tape (and, by the early 1950's, punch cards). It was tabulated using vacuum tubes and state-of-the-art circuits then either printed out or stored on more magnetic tape.

Mauchly and Eckert began building UNIVAC I in 1948 and a contract for the machine was signed by the Census Bureau on March 31, 1951, and a dedication ceremony was held in June of that year. UNIVAC I was soon used to tabulate part of the 1950 population census and the entire 1954 economic census. Throughout the 1950's, UNIVAC also played a key role in several monthly economic surveys. The computer excelled at working with the repetitive but intricate mathematics involved in weighting and sampling for these surveys.

UNIVAC I, as the first successful civilian computer, was a key part of the dawn of the computer age. Despite early delays, the UNIVAC program at the Census Bureau was a great success. The Bureau purchased a second UNIVAC I machine in the mid-1950's, and two UNIVAC 1105 computers for the 1960 census.

Census Bureau officials attended the dedication of UNIVAC I at the Eckert-Mauchly Laboratory in Philadelphia, PA, on June 14, 1951. Learn more about the ceremony from the June 22, 1951, Census Bulletin.